Gender, sex and complex PTSD clinical presentation: a systematic review

ABSTRACT

Background: Post-traumatic stress disorder (PTSD) prevalence and clinical presentation reportedly vary with gender and/or sex. Equivalent complex PTSD (CPTSD) research is in its relative infancy and to date no systematic review has been conducted on this topic.

Objective: To systematically review the literature and provide a narrative addressing the question of whether gender and/or sex differences exist in CPTSD prevalence and clinical presentation.

Method: Embase, PsycINFO, PTSDpubs, PubMed, Web of Science, EThOS and Google Scholar were searched. Twelve papers were eligible for inclusion. Data were extracted and synthesised narratively.

Results: Four themes were identified: (i) the reporting of gender and/or sex; (ii) index trauma; (iii) CPTSD prevalence rates; and (iv) CPTSD clinical presentation. Findings were mixed. Nine papers reported prevalence rates: eight found no gender and/or sex differences; one found higher diagnostic rates among women and/or females. Four papers reported clinical presentation: one reported higher cluster-level scores among women and/or females; two used single gender and/or sex samples; and one found higher scores in two clusters in men and/or males. Most papers failed to report in gender- and/or sex-sensitive ways.

Conclusions: Gender- and sex-sensitive research and clinical practice is needed. Awareness in research and clinical practice is recommended regarding the intersect between identity and the experience and expression of complex trauma.

HIGHLIGHTS

• This narrative review aims to establish whether gender and/or sex differences exist in complex post-traumatic stress disorder diagnosis rates and clinical presentation.

• Most papers adopted a binary approach to sex and gender.

• Most papers reported no difference in overall diagnosis rates, and few papers reported mixed findings regarding CPTSD presentation.

1. Introduction

The American Psychiatric Association’s fifth edition of the Diagnostic and Statistical Manual (DSM-5; APA, 2013) and the World Health Organisation’s 11th edition of the International Classification of Diseases (ICD-11; WHO, 2019) diverge in their conceptualisations of post-traumatic stress disorder (PTSD).

The DSM-5 conceptualises PTSD as a broad diagnosis characterised by trauma re-experiencing, avoidance, negative alterations in cognitions and mood and hyperarousal (APA, 2013). The ICD-11 outlines two ‘sibling’ diagnoses: PTSD and complex PTSD (CPTSD) (Karatzias et al., 2017). PTSD encompasses re-experiencing, avoidance and persistent threat (hyperarousal and hypervigilance); CPTSD includes the above criteria plus three pertaining to disturbances in self-organisation (DSO): emotion dysregulation, negative self-concept and interpersonal difficulties (Hyland, Shevlin, et al., 2018). DSO items intend to encompass the profound difficulties related to prolonged or repeated trauma, often interpersonal in nature, from which escape is difficult (e.g. child abuse, captivity) (Karatzias et al., 2017). Although dropped in the DSM-5 in favour of the broader PTSD conceptualisation, the diagnostic category ‘disorders of extreme stress not otherwise specified’ (DESNOS) in the DSM-4 was thought to reflect trauma of this nature (Friedman, 2013).

Research into the construct validity of ICD-11 PTSD and CPTSD diagnoses supports distinctions between the two in adult clinical samples (Hyland, Shevlin, et al., 2018), university undergraduates (Rink & Lipinska, 2020), homeless adults (Armstrong et al., 2020), foster children (Haselgruber et al., 2019), adult survivors of childhood institutional abuse (Knefel et al., 2015) and refugees (Vang et al., 2020). CPTSD diagnoses are strongly associated with childhood trauma and functional impairment (Karatzias et al., 2017; Karatzias et al., 2021; Rink & Lipinska, 2020). Comparisons between DSM-5 PTSD and ICD-11 PTSD and CPTSD diagnosis rates are not always consistent, with some evidence for comparable rates (Kuester et al., 2017) and some for higher rates according to DSM-5 criteria (Heeke et al., 2020; Hyland, Shevlin, et al., 2018). This might be expected given the intentional broadness of the DSM-5 diagnostic criteria (Hyland, Shevlin, et al., 2018).

Factors pertinent to PTSD diagnosis rates include gender and sex (Kimerling et al., 2018). Lifetime PTSD prevalence is reportedly higher among women (Kimerling et al., 2018) and UK figures show that women are more likely to screen positive for PTSD in all age categories except 55–64 (PTSD UK, 2023). Research suggests that a combination of pre-, peri- and posttraumatic risk factors more common in females may help to explain sex differences in PTSD severity (Christiansen & Hansen, 2015). Found to significantly mediate sex-PTSD severity association when combined, females reported higher levels of depression, physical anxiety sensitivity, peritraumatic fear, horror and helplessness, panic, dissociation, feeling let down and negative posttraumatic cognitions about the self and the world (Christiansen & Hansen, 2015). Gender factors (e.g. masculine ideals and masculine gender role stress [the subjective stress from not conforming to said ideals]) and sex factors (e.g. hormones) are highlighted as contributors to sex differences in PTSD in another study (Christiansen & Berke, 2020). Such risk factors may also be relevant considerations in the development of CPTSD.

PTSD clinical presentation may also vary with gender: men may experience more irritability and reckless behaviour (Green, 2003) and women may experience more avoidance and hyperarousal (Fullerton et al., 2001). Whether figures pertain to sex (based on anatomy and typically assigned at birth [Stonewall, 2023]) or gender (one’s own identity and internal sense of self, which exists on a non-binary spectrum [Cameron & Stinson, 2019] and which may or may not correspond with sex [Stonewall, 2023]), however, is not always clear, and research tends to adopt a binary approach to both (Olff, 2017). Prevalence rates among gender non-binary individuals may be higher still, with reported rates of up to 42% (Livingston et al., 2020). Gender non-binary individuals reportedly experience higher rates of sexual abuse, harassment and trauma exposure than cisgender individuals (whose gender identity corresponds with sex assigned at birth) (Lefevor et al., 2019), so elevated PTSD diagnoses may not be surprising.

Research into CPTSD prevalence rates is in its relative infancy given the recency of this diagnostic classification (Hyland, Shevlin, et al., 2018). Women may be more likely to experience sexual and intimate violence (Kimerling et al., 2018; Olff, 2017), more likely, as noted above, to experience a combination of risk factors associated with trauma severity and may be more at risk of receiving this diagnosis (Hyland et al., 2017). Such increased risk may lead to sex and/or gender differences in prevalence. Whether there are routine sex and/or gender differences or similarities in prevalence and clinical presentation of CPTSD diagnoses, however, is unclear and to date no systematic review exists on this topic.

1.1. Current review

To address this gap in the literature, this paper aimed to systematically review and synthesise CPTSD literature to establish whether gender and/or sex differences exist in the prevalence and clinical presentation of this diagnosis. Such knowledge would have significant implications for diagnostic tools, therapeutic approach and gender-responsive services (Hyland, Shevlin, et al., 2018). The review differentiated between gender and sex in line with the definitions above (Cameron & Stinson, 2019; Stonewall, 2023), wherein gender is conceptualised as a non-binary construct. The inclusion of non-binary individuals in the current review, therefore, was led by this conceptualisation of gender as a non-binary construct. Search terms were generated, and relevant literature was reviewed and synthesised, accordingly.

2. Method

2.1. Search strategy

Searches were conducted between 28th April and 1st May 2023. Embase, PsycINFO, PTSDpubs, PubMed, Web of Science, EThOS and Google Scholar were searched. Titles, abstracts and key words were searched using a core search strategy adapted to each database structure. Searches were filtered by publication date (2013 to present to include the 2013 DSM-5 and 2018 ICD-11 publication dates). The strategy was overseen and approved by a subject specialist librarian. Search terms are below.

Search terms in Table 1 were used for all databases bar EThOS and Google Scholar. The searches ‘gender differences in complex PTSD presentation’, ‘sex differences in complex PTSD presentation’ and ‘gender differences in complex PTSD symptoms’ were employed for these databases owing to their different search structure. Established from scoping searches, the first four pages of Google Scholar results were searched.

Table 1.

Search terms.

Review element	Search terms
Gender, Sex	1. Gender 2. Sex 3. Nonbinary 4. Male 5. Female 6. Men 7. Women 8. Gender AND differences
CPTSD	9. Complex PTSD 10. CPTSD 11. C-PTSD 12. Complex posttraumatic* 13. Complex symptoms of PTSD 14. Complex trauma 15. DESNOS
Clinical presentation	16. Symptom* 17. Presentation 18. Phenomenology 19. Symptom AND profile
Combination terms	20. 1 OR 2 OR 3 OR 4 OR 5 OR 6 OR 7 OR 8 21. 9 OR 10 OR 11 OR 12 OR 13 OR 14 OR 15 22. 16 OR 17 OR 18 OR 19 23. 20 AND 21 AND 22

2.2. Eligibility criteria

Study inclusion criteria were: (i) child or adult clinical or non-clinical samples; (ii) diagnosis of CPTSD or DESNOS; (iii) use of accepted diagnostic tool (see Table 2); (iv) clear, specific discussion of CPTSD presentation; (v) CPTSD presentation separated by gender or sex, or in one gender or sex only; (vi) qualitative or quantitative empirical study; (vii) any location; (viii) written in or translated to English; and (ix) published 2013 onwards (see Table 2).

Table 2.

Eligibility criteria.

	Inclusion criteria	Exclusion criteria
Sample	Child or adult, clinical or non-clinical	–
Diagnosis	Diagnosis of CPTSD or DESNOS*	No diagnosis of CPTSD or DESNOS
Measures	ITQ, ICD-TQ, SIDES, SIDES-A	No use of accepted measure
Content	Clear, specific discussion of CPTSD presentation	CPTSD presentation not specifically and clearly discussed
	CPTSD presentation separated by gender or sex or in one gender or sex only	CPTSD presentation not separated by gender or sex
Methodology	Qualitative or quantitative empirical study	Not an empirical study
Location	Any	–
Language	Written in or translated to English	Not written in or translated to English
Date	Published 2013 onwards	Published before 2013

Notes: ICD-TQ = ICD-11 Trauma Questionnaire (Karatzias et al., 2016). ITQ = International Trauma Questionnaire (Cloitre et al., 2018). SIDES = Structured Interview for Disorders of Extreme Stress and SIDES-A = Structured Interview for Disorders of Extreme Stress-Adolescent Version (Pelcovitz et al., 1997).

*DESNOS was included due to the construct overlap with CPTSD (Friedman, 2013).

2.3. Study selection

The initial search identified 4597 papers. Titles and abstracts were imported into Covidence, an online review site, and duplicates were automatically removed (n = 1173). Titles and abstracts were screened and excluded if they did not clearly report on gender and/or sex and CPTSD (n = 3388). Papers were retained at this stage if there was insufficient evidence to exclude them. Inter-rater reliability with an independent second reviewer was conducted on 10% of titles/abstracts with 97.4% agreement. Discussion took place between first author and independent reviewer to reach consensus. A total of 36 papers were subject to full text review and assessed for eligibility, of which 24 were excluded (Figure 1; Appendix 1). Inter-rater reliability was conducted at full text review on 10% of papers with 100% consensus. A total of 12 papers were eligible for inclusion (Figure 1; Appendix 2).

Figure 1.

PRISMA flowchart.

2.4. Quality assessment

Quality of included papers was assessed by the first author using the Mixed Methods Appraisal Tool (MMAT) (Hong et al., 2018). Suitable for qualitative, quantitative and mixed methods studies, the MMAT assesses quality against five criteria relevant to each of five study designs. The tool encourages a descriptive summary (see Appendix 3) of each criterion’s rating to provide context rather than for exclusion purposes. To aid interpretation, papers were additionally scored 0 where a criterion was not met and 1 where a criterion was met. Scores were converted into percentages (see Table 3).

Table 3.

MMAT quality assessment scores.

Criterion
Study	4.1	4.2	4.3	4.4	4.5	Overall %
Charak et al. (2023)	1	0	1	0	1	60
Cloitre et al. (2019)	1	1	1	0	1	80
de Vries et al. (2018)	1	0	1	0	0	40
Fernández-Fillol et al. (2021)	1	0	1	1	1	80
Giarratano et al. (2020)	1	1	1	1	1	100
Gilbar et al. (2018)	1	0	0	0	1	40
Hecker et al. (2018)	1	1	1	1	1	100
Ho et al. (2021)	1	1	1	0	1	80
Hyland, Ceannt, et al. (2018)	1	0	1	0	1	60
Karatzias et al. (2019)	1	1	1	1	1	100
McGinty et al. (2021)	1	1	0	0	1	60
Søegaard et al. (2021)	1	0	0	1	1	60

2.5. Data extraction

Data were extracted from eligible papers by the first author. Extracted data included authors, country, study focus, sample, gender or sex, participant demographics, relevant measures, trauma type and key relevant findings (see Tables 4 and 5).

Table 4.

Data extraction.

Author(s)	Country	Focus	Sample	Gender or sex	Demographics	Relevant measures	Relevant findings	Quality rating %
Charak et al. (2023)	Spain	Associations between lifetime trauma exposure, minority stress and CPTSD among LGBTQ + adults	Community sample of LGBTQ + adults with cumulative lifetime trauma exposure (N = 225)	Gender – specifies cisgender, gender diverse and transgender participants	Age: 18–60 (M = 31.35). 33.3% women (incl. trans women); 46.3% men (incl. trans men); 13.5% gender non-binary; 6.8% ‘gender identity not listed’. Ethnicity: 82.5% White; 10.3% Latinx; 2.2% Biracial/Multiracial; 0.4% Asian, 4.5% ‘additional category not listed’	ITQ	19.1% met diagnostic criteria for CPTSD (n = 43): n = 23 gender diverse or transgender, n = 20 cisgender Similar rates of CPTSD diagnoses in cisgender and gender diverse or transgender participants Cissexism related to gender expression was positively associated with DSO factors (r = .365, p < .01)	60%
Cloitre et al. (2019)*	USA*	Prevalence of ICD-11 PTSD and CPTSD diagnoses	Nationally representative household sample of community adults (N = 1839)	Specifies sex – refers to ‘male’ and ‘female’ in demographics and ‘men’ and ‘women’ in results	Age: 18–70 (M = 44.50). 52% F; 48% M. Ethnicity: 63.8% White; 36.2% ‘non-White’	ITQ, LEC	Women had significantly higher rates of CPTSD diagnoses than men (OR = 1.82, 95% CI [1.10, 3.01])	80%
de Vries et al. (2018)	USA	Relationship between homelessness, gender and PTSD and CPTSD diagnoses	Homeless adults (N = 90)	Specifies gender – refers to ‘male’ and ‘female’ in demographics and ‘men’ and ‘women’ in results	Age: 18–61 (M = 37.64). 58% F; 42% M. Ethnicity: 37% White; 28.9% Hispanic; 18.9% African American; 8% ‘other’; 7.8% did not respond	SIDES	No significant relationship found between gender and CPTSD or DESNOS scores	40%
Fernández-Fillol et al. (2021)	Spain	CPTSD in survivors of IPV	Adult women survivors of IPV (N = 162)	Not specified – paper refers to ‘women’	Age: 20–75 (M = 41.42). 100% women. Ethnicity: data not provided	ITQ	39.5% met CPTSD diagnostic criteria 85.2% met criteria for AD; 64.8% met criteria for DR; 61.1% met criteria for NSC High fear was associated with DR (OR = 1.27, 95% CI [1.03–1.57]) Low resilience was associated with AD (OR = .93, 95% CI [0.89–0.97]), NSC (OR = 0.93, 95% CI [0.90–0.96]) and DR (OR = 0.96, 95% CI [0.93–0.99])	80%
Giarratano et al. (2020)	USA	Gender differences in CPTSD symptoms, mental health and substance abuse in incarcerated adults	Incarcerated adults (N = 497)	Specifies gender – refers to ‘men’ and ‘women’ in paper	Age: M = 31.64. 39.4% women; 60.6% men. Ethnicity: 43.1% White; 34.8% Black; 21.5% Hispanic; 0.6% missing	SIDES	Women had significantly higher levels of CPTSD symptomatology than men, t (444) = 2.15, p = .032, d = .20, 95% CI = [−0.02, −0.38]	100%
Gilbar et al. (2018)	Israel	ICD-11 CPTSD among Israeli male perpetrators of IPV	Israeli male perpetrators of IPV (N = 234)	Not specified – paper only refers to ‘males’	Age: no data. 100% M. Ethnicity: no data	ITQ, LEC-5	Frequency of CPTSD symptom endorsements were: 53% feelings easily hurt (AD3); 48.7% guilt (NSC4); 42.1% long time to calm (AD2); 32.3% reckless behaviour (AD5); 31.4% uncontrollable anger (AD4); 30.5% intense reactions (AD1); 30.4% numb (AD6); 25.7% difficulty feeling pleasure (AD7); 25.1% difficultly staying close to others (DR2); 24.9% shame (NSC3); 23.2% world is distant (AD8); 23.2% failure (NSC1); 21.3% cut-off from others (DR1); 20.3% avoiding relationships (DR3); 17.9% worthless (NSC2); 10.7% feeling outside of body (AD9)	40%
Hecker et al. (2018)	Switzerland	PTSD and CPTSD symptoms and traumatic experiences among refugees	Adult refugees resettled in Switzerland (N = 94)	Specifies gender – refers to ‘male’ and ‘female’ in paper	Age: 18–61 (M = 31.60). 14.9% F; 85.1% M. Ethnicity: no data	ITQ, HTQ-5	21.3% (n = 20) met diagnostic criteria for CPTSD Gender not significantly associated with DSO symptom severity, (F (1,86) = 1.10, p = .297)	100%
Ho et al. (2021)*	Ireland*	Gender-specific examination of ICD-11 CPTSD and psychosis	Community sample of nationally representative adults (N = 1020)	Specifies gender in title and results, but also refers to sex in results tables – appears to use sex and gender interchangeably (refers to ‘male’ and ‘female’ in paper)	Age: 18–87 (M = 43.10). 51% F; 49% M. Ethnicity: no data	ITQ, ITEM	Females had significantly higher levels of CPTSD symptoms than males (t (1018) = 5.81, p < .001, d = .36) No significant differences in overall CPTSD diagnoses between females and males (p = .13)	80%
Hyland, Ceannt, et al. (2018)	Lebanon	PTSD and CPTSD diagnoses among Syrian refugees living in Lebanon	Syrian refugees living in Lebanon (N = 101)	Specifies gender – refers to ‘male’ and ‘female’ in paper	Age: M = 33.02. 80.2% F; 19.8% M. Ethnicity: no data	ITQ Arabic Version	No significant gender differences in diagnostic rates of CPTSD (χ2 = .031, df = 1, p = .578, OR = 1.31)	60%
Karatzias et al. (2019)*	UK*	ICD-11 PTSD and CPTSD diagnostic risk factors and comorbidity	Trauma-exposed population-based sample of adults (N = 1051)	Specifies sex – refers to ‘male’ and ‘female’ in paper	Age: 18–90 (M = 47.18). 68.4% F; 31.6% M. Ethnicity: no data	ITQ, LEC-5	12.9% of N met CPTSD diagnostic criteria No significant relationship between sex and CPTSD diagnosis	100%
McGinty et al. (2021)*	Israel, Ireland*, USA*, UK*	Differences in ICD-11 PTSD and CPTSD	Nationally representative community sample of adults (Israel N = 1003)	Specifies sex – refers to ‘male’ and ‘female’ in paper	Age: 18–70 (M = 40.62). 51.7% F; 48.3% M. Ethnicity: no data	ITQ, LEC-5	No significant relationship between sex and CPTSD diagnosis in Israel sample	60%
Søegaard et al. (2021)	Norway	Gender differences in trauma symptoms after victimisation and accidental traumas	Community sample of traumatised adults (N = 110)	Specifies gender – refers to ‘men’ and ‘women’	Age: 18–60 (M = 40.4). 61.8% women; 38.2% men. Ethnicity: no data	SIDES, LEC	No significant relationship between gender and overall DESNOS diagnosis Men had significantly higher scores in 2 out of 7 DESNOS clusters: negative self-perception (p = .043) and alterations in systems of meaning (p = .003) In Ps with VT, men had higher negative self-perception (p = .022) and alterations in systems of meaning (p = .006); in Ps with AT, women had higher scores on affect and impulses (p = .011)	60%

Notes: AD = affect dysregulation. DR = disturbances in relationships. DSO = disturbances in self-organisation. IPV = intimate partner violence. ITEM = International Trauma Exposure Questionnaire (International Trauma Consortium). ITQ = International Trauma Questionnaire (Cloitre et al., 2018). LEC-5 = Life Events Checklist for DSM-5 (Weathers et al., 2013). NACM = negative alterations in cognition and mood. NSC = negative self-concept. SIDES = Structured Interview for Disorders of Extreme Stress (Pelcovitz et al., 1997).

*Papers use same samples: only findings from McGinty et al.’s (2021) Israel sample, which does not overlap, reported in the current review.

Table 5.

Data extraction: trauma type.

	All	Women or females	Men or males	Significant differences (where included in paper)
Charak et al. (2023)	73.3% reported 2 + traumas: 51.5% unwanted sexual experience; 38.7% physical assault; 30.2% sexual assault; 28.4% life-threatening illness/injury; 28% transportation accident; 27.1% sudden unexpected death of someone close; 18.4% severe human suffering; 16.9% natural disaster; 13.8% sudden violent death; 12.6% assault with weapon; 11.1% fire/explosion; 6.7% serious accident; 4% exposure to toxic substance; 1.8% combat/warzone; 1.8% captivity	–	–	–
Cloitre et al. (2019)	Not specified	Not specified	Not specified	–
de Vries et al. (2018)	–	Only data on childhood abuse collected: 53.8% childhood emotional abuse; 52.9% childhood sexual abuse; 52.9% childhood physical abuse	Only data on childhood abuse collected: 41.2% childhood physical abuse; 38.2% childhood emotional abuse; 23.5% childhood sexual abuse	–
Fernández-Fillol et al. (2021)	–	98.2% psychological violence, 71% physical violence, 33.3% sexual violence, 49.9% ‘other trauma’, 27.8% ‘other interpersonal trauma’	–	–
Giarratano et al. (2020)	–	60.2% childhood abuse, 13.3% adult interpersonal trauma, 5.1% childhood loss/caregiver separation, 5.1% childhood accident/illness/disaster, 3% adult accident/illness/disaster, 2% adult witness trauma, 11.2% no traumatic experiences	41.5% childhood abuse, 12.3% adult interpersonal trauma, 8.3% childhood accident/illness/disaster, 7.3% childhood loss/caregiver separation, 5% adult accident/illness/disaster, 4.3% adult witness trauma, 21.3% no traumatic experiences	Women were significantly more likely than men to have experienced childhood abuse (p < .01) Child abuse history mediated association between gender and CPTSD, B = 1.76, p < .001, 99% CI = [0.789, 2.743]
Gilbar et al. (2018)	Not specified	Not specified	Not specified	–
Hecker et al. (2018)	–	71.4% lack of food/water, 57.1% lack of shelter, 57.1% warzone exposure, 57.1% violent attack by stranger, 42.9% natural disaster, 42.9% forced separation from family, 36.1% serious accident/fire/explosion, 36.1% murder of family member/friend, 36.1% violent attack by family member, 28.6% torture, 28.6% enforced isolation from others, 28.2% witness murder of 1 + strangers, 21.4% sexual assault by stranger, 21.4% sexual assault by family member, 21.4% imprisonment, 21.4% ill-health without medical care, 14.3% unnatural death of family member/friend, 7.1% life-threatening illness	76.3% lack of shelter, 75% lack of food/water, 75% warzone exposure, 72.5% serious accident/fire/explosion, 70% violent attack by stranger, 63.8% imprisonment, 62.5% torture, 61.3% witnessed murder of 1 + strangers, 56.3% murder of family member/friend, 51.3% unnatural death of family member/friend, 47.5% enforced isolation from others, 47.5% forced separation from family, 40% ill-health without medical care, 27.5% natural disaster, 25% violent attack by family member, 20% life-threatening illness, 8.8% sexual assault by stranger, 3.8% sexual assault by family member	–
Ho et al. (2021)	–	65% emotional abuse, 56.5% unloved/emotional rejection, 53.8% life-threatening illness/accident-other, 45.2% sexual harassment, 44.2% physical/emotional neglect, 40% someone close died in awful manner, 39% bullied, 33.5% physical assault by parent/guardian, 32.1% physical assault by someone else, 24.2% witnessed extreme suffering/death, 21.9% stalked, 18.6% sexual assault by someone else (not parent/guardian), 17.9% life-threatening accident, 15.8% life threatened with weapon, 12.1% life-threatening illness-self, 6.5% natural disaster, 6.4% life-threatening human-caused disaster, 5% war/combat, 4.6% sexual assault by parent/guardian, 4.6% torture/captivity, 2.7% caused extreme suffering/death	55.6% emotional abuse, 49.8% life-threatening illness/accident-other, 46.8% physical assault by someone else (not parent/guardian), 39.4% unloved/emotional rejection, 37.4% someone close died in awful manner, 36.8% bullied, 34.4% physical/emotional neglect, 28.4% physical assault by parent/guardian, 27.6% life-threatening accident, 25.8% life threatened with weapon, 25% witnessed extreme suffering/death, 16.4% sexual harassment, 16.2% life-threatening illness-self, 14.6% stalked, 10.6% life-threatening human-caused disaster, 9.6% war/combat, 9.6% natural disaster, 8.8% sexual assault by someone else (not parent/guardian), 6.8% torture/captivity, 6.4% caused extreme suffering/death, 4.6% sexual assault by parent/guardian	Females were significantly more likely than males to have been sexually assaulted by someone other than parent/guardian, sexually harassed, stalked, emotionally abused, emotionally rejected/unloved and physically/emotionally neglected (all p < .001) Males were significantly more likely than females to have experienced life threatened with a weapon, physical assault by someone other than parent/guardian, life-threatening accident (all p < .001), war/combat (p = .005), causing extreme suffering/death to other (p = .004) and life-threatening human-made disaster (p = .015)
Hyland, Ceannt, et al. (2018)	18.5% forced displacement, 10.2% exposure to bomb blasts, 10.2% sudden unexpected death of loved one, 7.4% exposure to warfare, 2.7% childhood sexual or physical abuse	–	–	–
Karatzias et al. (2019)	Only data on most common childhood and adulthood traumatic event reported: 32.4% physical assault (childhood), 47.4% sudden unexpected death of loved one (adulthood)	–	–	–
McGinty et al. (2021) – Israel sample	Not specified	Not specified	Not specified	–
Søegaard et al. (2021)	–	Victimisation trauma: 27.9% sexual assault or rape; 27.9% physical assault; 13.2% assault with lethal weapon; 7.4% torture or captivity; 2.9% unwanted/uncomfortable sexual experience; 2.9% combat/warzone; 1.5% witnessed homicide. Accidental trauma: 4.4% accidental fire/explosion; 7.4% accident (transportation or other); 4.4% sudden accidental death of close person	Victimisation trauma: 26.2% combat/warzone; 26.2% physical assault; 11.9% assault with lethal weapon; 11.9% sexual assault or rape; 4.8% torture or captivity; 2.4% witnessed homicide. Accidental trauma: 9.5% accident (transportation or other); 4.8% sudden accidental death of close person; 2.4% severe human suffering	Women were significantly more likely to have experienced sexual assault (p = .04) Men were significantly more likely to have experienced combat or warzone (p = .04)

2.6. Data synthesis

Data synthesis was conducted by the first author using a process akin to thematic analysis. Key relevant data were summarised during data extraction. Themes were identified across the summarised data in relation to gender, sex and CPTSD diagnosis. Themes captured trends in the research pertaining to gender and/or sex and CPTSD. Narrative synthesis was used to describe themes in the data.

3. Results

3.1. Overview

Papers spanned the United States of America (n = 3), Spain (n = 2) and one each from Ireland, Israel, Lebanon, Norway, the United Kingdom and Switzerland. The final paper (McGinty et al., 2021) used samples from Ireland, Israel, the USA and the UK These appeared to be the same samples as the papers from each individual country bar Israel. This paper was included in the current review, but only findings from the Israel sample were reported. Samples were mostly community adults (n = 6). Remaining papers included refugee samples (n = 2), homeless samples (n = 1), incarcerated adults (n = 1) and perpetrators (n = 1) and survivors (n = 1) of intimate partner violence (IPV). Ages ranged from 18 to 90. Sample size varied from 15 to 1839. Most (n = 8) did not provide data on participant ethnicity. Of those that did (n = 4), White was the majority. Quality assessment ratings ranged from 40% to 100%.

Five papers explored gender and/or sex differences. Five had gender and/or sex as one component part but not the focus (i.e. in general prevalence studies). The remaining two papers indirectly studied gender and/or sex (i.e. the sample was single gender or sex, so this element was implicit). Nine papers studied ICD-11 CPTSD and three studied DESNOS or ‘CPTSD’ measured with the SIDES. Most (n = 8) used self-report measures such as the ITQ. Three employed interviews such as the SIDES.

Data synthesis anchored to the research question led to the identification of four themes pertaining to gender and/or sex: (i) how gender and/or sex were reported; (ii) index trauma(s); (iii) CPTSD prevalence rates; and (iv) CPTSD clinical presentation (see Table 6 for papers and themes). Results in the current review adopted gender- and/or sex-based language consistent with each included paper.

Table 6.

Main themes and relevant studies.

Theme	Relevant papers	Details
Reporting of gender and/or sex	All papers:
	Charak et al. (2023)	Specifies gender
	Cloitre et al. (2019)	Specifies sex
	de Vries et al. (2018)	Specifies gender
	Fernández-Fillol et al. (2021)	Not specified
	Giarratano et al. (2020)	Specifies gender
	Gilbar et al. (2018)	Not specified
	Hecker et al. (2018)	Specifies gender
	Ho et al. (2021)	Uses gender and sex interchangeably
	Hyland, Ceannt, et al. (2018)	Specifies gender
	Karatzias et al. (2019)	Specifies sex
	McGinty et al. (2021)	Specifies sex
	Søegaard et al. (2021)	Specifies gender
Index trauma(s) by gender and/or sex	de Vries et al. (2018) Fernández-Fillol et al. (2021) Giarratano et al. (2020) Hecker et al. (2018) Ho et al. (2021) Søegaard et al. (2021)	See Table 5 for all details
CPTSD prevalence rates by gender and/or sex	Charak et al. (2023)	Similar CPTSD diagnostic rates among cisgender and gender diverse Ps
	Cloitre et al. (2019)	Higher CPTSD diagnostic rates among women
	de Vries et al. (2018)	No relationship between gender and CPTSD scores
	Hecker et al. (2018)	No relationship between gender and DSO severity
	Ho et al. (2021)	Higher CPTSD symptom levels among females, but no gender difference in CPTSD diagnoses
	Hyland, Ceannt, et al. (2018)	No gender difference in CPTSD diagnostic rate
	Karatzias et al. (2019)	No relationship between sex and CPTSD diagnosis
	McGinty et al. (2021)	No relationship between sex and CPTSD diagnosis in Israel sample
	Søegaard et al. (2021)	No relationship between gender and overall DESNOS diagnosis
CPTSD clinical presentation by gender and/or sex	Fernández-Fillol et al. (2021)	Approx. % of women met DSO criteria: 85% AD; 65% DR; 61% NSC
	Giarratano et al. (2020)	Higher CPTSD symptoms in women
	Gilbar et al. (2018)	5 highest symptoms (approx. %): 53% feelings easily hurt (AD3); 49% guilt (NSC4); 42% long time to calm down (AD2); 32% reckless behaviour (AD5); 31% uncontrollable anger (AD4)
	Søegaard et al. (2021)	Higher scores in two DESNOS clusters in men (negative self-perception and alterations in systems of meaning)

3.2. Reporting of gender and/or sex

Six papers referred to ‘gender’ differences, three referred to ‘sex’ differences, two did not specify and one used ‘gender’ and ‘sex’ interchangeably. Of the papers that specified gender, only one (Charak et al., 2023) differentiated between cisgender, gender diverse and transgender individuals. This paper scored 60% in quality assessment. Remaining papers adopted a binary approach to gender and sex, where only ‘male’ and ‘female’ or ‘men’ and ‘women’ were reported. Bar Charak et al. (2023), no papers specified how participants were asked about gender and/or sex, and whether participants were provided options or asked about one or the other or both.

3.3. Index trauma(s) by gender and/or sex

Nine papers reported index trauma(s), six of which reported index trauma(s) by gender and/or sex. Of those six, three conducted statistical analyses on trauma type by gender and/or sex. Women were significantly more likely to have experienced childhood abuse in Giarratano et al. (2020), but abuse type was not specified. Child abuse mediated the association between gender and CPTSD. This paper scored 100% in quality assessment.

Number of experiences of sexual assault, sexual harassment, being stalked, emotional abuse and physical or emotional neglect were all significantly higher in females in another paper (Ho et al., 2021). Males reported significantly higher rates of physical assault, life-threatening accident or disaster, life threatened with a weapon, war/combat and causing extreme suffering to someone else (Ho et al., 2021). This paper scored 80% in quality assessment. Søegaard et al. (2021) reported a similar finding: sexual assault was experienced by significantly more women; experiences of combat were significantly higher among men. This paper scored 60% in quality assessment.

Three papers reported index trauma(s) by gender and/or sex without statistical analyses. In de Vries et al. (2018), who reported childhood abuse, most women reported emotional abuse, then sexual abuse and physical abuse. Among men, physical abuse was most common and sexual abuse least common.

Fernández-Fillol et al. (2021) had an all-women sample of IPV survivors. Most experienced psychological violence; nearly three-quarters experienced physical violence; a third experienced sexual violence and nearly half also reported ‘other trauma’. In Hecker et al.’s (2018) paper with refugee participants, there were few gender and/or sex differences in the most reported events (lack of shelter/food/water, warzone exposure). However, sexual assaults by a stranger or a family member were each endorsed by 21.4% of females compared to 8.8% and 3.8% of males, respectively.

3.4. CPTSD prevalence rates by gender and/or sex

Nine papers reported CPTSD diagnostic rates by gender and/or sex. There were two subthemes: no gender and/or sex differences, and higher rates among women or females. Eight studies found no gender and/or sex differences (Charak et al., 2023; de Vries et al., 2018; Hecker et al., 2018; Ho et al., 2021; Hyland, Ceannt, et al., 2018; Karatzias et al., 2019; McGinty et al., 2021 [Israel sample]; Søegaard et al., 2021). Most of these papers scored between 60% and 100% in quality assessment (one scored 40%).

Although Ho et al. (2021) found no gender difference in overall CPTSD diagnostic rates, they reported higher cluster-level scores among females, suggesting a symptom-level difference that did not reach diagnostic threshold. Charak et al. (2023) did not report diagnostic rates by gender but reported similar rates among cisgender and gender diverse participants more broadly. The remaining paper reported significantly higher CPTSD diagnostic rates among women (Cloitre et al., 2019). This paper scored 80% in quality assessment.

3.5. CPTSD clinical presentation by gender and/or sex

Four papers reported CPTSD clinical presentation by gender and/or sex. Findings were mixed. Giarratano et al. (2020) reported higher overall CPTSD symptoms among women but did not specify which symptoms. In Søegaard et al. (2021), where there were no overall differences in DESNOS scores, men had significantly higher cluster scores for negative self-perception (e.g. shame and guilt) and alterations in systems of meaning (e.g. despair, negative change in existential beliefs). Fernández-Fillol et al. (2021) and Gilbar et al. (2018) both used single gender and/or sex samples. Percentages of women meeting DSO criteria were: 85% affective dysregulation (AD); 65% disturbances in relationships (DR); and 61% negative self-concept (NSC) (Fernández-Fillol et al., 2021). In Gilbar et al. (2018), the five most reported CPTSD items were feelings easily hurt (AD3), guilt (NSC4), long time to calm down (AD2), reckless behaviour (AD5) and uncontrollable anger (AD4). Although direct comparisons from these findings were not possible, there were similarities as AD scores were highest in the women-only sample and four of the five AD items featured in the top five endorsed DSO items in the male-only sample.

4. Discussion

This was the first known paper to systematically review and synthesise literature on gender, sex and CPTSD to establish whether gender and/or sex differences exist in the prevalence and clinical presentation of this diagnosis. Themes identified from data synthesis were the reporting of gender and/or sex, index trauma, CPTSD prevalence rates and CPTSD clinical presentation.

4.1. Reporting of gender and/or sex

Only one of the 12 papers included non-binary gender options and differentiated between cisgender and gender diverse participants (Charak et al., 2023). Remaining papers employed a mix of language: some used ‘gender’ and others ‘sex’; some ‘male’ and ‘female’; and some ‘men’ and ‘women’. Most papers used these categories interchangeably, and one used ‘gender’ and ‘sex’ interchangeably, suggesting a conflation of the two constructs. Interchangeable use is not necessarily a problem in of itself had all participants’ genders corresponded with their sex, but no papers (bar Charak et al., 2023) specified how participants were asked about gender and sex and most papers adopted a binary approach to both. This supports findings that researchers often mix sex and gender terminology (Westbrook & Saperstein, 2015).

This is problematic given research that affirms that both gender and sex are non-binary constructs (Cameron & Stinson, 2019). In their review, Cameron and Stinson (2019) highlight that psychological research still largely adopts a binary approach to gender. They cite ethical principles and exclusionary practices as pertinent concerns. Indeed, Olff (2017) strongly advocates for more gender- and sex-sensitive research (regarding trauma research specifically, although this would apply more broadly).

4.2. Index trauma(s) by gender and/or sex

Rates of sexual trauma were either significantly or, where statistical analyses were not conducted, consistently higher among women and/or females. This corroborates previous findings (Kimerling et al., 2018; Olff, 2017) and is significant as these interpersonal traumas are strongly associated with many CPTSD diagnostic criteria such as shame, low self-esteem, emotional dysregulation and attachment difficulties (Karatzias et al., 2017).

Factors related to trauma type and the reporting of traumatic experiences are worth consideration. Research with men who experienced sexual assault highlighted barriers to disclosure (Donne et al., 2018; Petersson & Plantin, 2019). Both studies reported themes of masculinity norms and gender roles in relation to disclosure. Petersson and Plantin (2019) highlighted the difficulties faced by men being perceived as ‘powerless victims of sexual violence’, as this violates traditional masculinity norms of power, assertiveness and strength. Donne et al. (2018) identified similar themes: men cited internalised masculinity norms, which perpetuate the idea that men who experience sexual violence are ‘weak’, as barriers to disclosure.

Gender norms and roles may also bias research towards studying and reporting sexual trauma among women and combat or motor vehicle collisions among men. Indeed, these align with dominant gender roles that masculinity encompasses aggression, thrill-seeking and risky behaviours and femininity encompasses submissiveness and sensitivity (Street & Dardis, 2018). If pervasive gender norms influence rates of disclosure by men via the denial of certain experiences that do not fit said norm, it is feasible that they also shape how research is conducted and on what research focuses. This would continue to perpetuate the perceived bias in trauma type by gender and/or sex. Both factors are likely to influence figures regarding gender-based experiences of trauma.

4.3. CPTSD prevalence rates by gender and/or sex

Most papers found no gender and/or sex differences in CPTSD prevalence, although one reported higher cluster-level CPTSD scores among females. One paper reported higher diagnostic rates among women.

Self-report measures were commonly used to capture CPTSD diagnostic status, which may be vulnerable to the influence of gender norms and roles. For example, men may underreport difficulties they experience following certain (gender norm-incongruent) traumatic experiences due to pervasive norms that perpetuate the idea that men must appear to be strong and unemotional (Donne et al., 2018). Donne et al. highlighted problematic correlates of such gender norms, such as the perceived lack of systems to facilitate the processing of such (gender norm-incongruent) trauma and related emotional responses in men, and societal narratives that perhaps are not ready to accept men as affected by such experiences (Donne et al., 2018). Women may similarly underreport difficulties they experience following gender norm-incongruent traumatic experiences. Both circumstances would inevitably influence prevalence rates.

Indeed, prevalence rates may be entirely accurate, which suggests that there are currently no consistent gender- and/or sex-based differences in CPTSD diagnostic rates. Given the pervasive gender norms discussed above, the norm-congruent trauma types with which they are associated and the possible problematic correlates of this (i.e. the denial of norm-incongruent trauma responses), one cannot help but wonder about the accuracy of prevalence rates when they exist within systems mediated by these context-dependent socially constructed stories about what constitutes trauma and how and in whom it manifests.

4.4. CPTSD clinical presentation by gender and/or sex

CPTSD clinical presentation was mixed. One paper found higher overall CPTSD symptoms among women, but did not specify which symptoms, and one found greater negative self-perception and alterations in systems of meaning among men. The remaining two papers both reported high affect dysregulation in their single gender and/or sex samples.

Despite the paucity of data regarding CPTSD presentation, feelings of shame and guilt and affect dysregulation items (e.g. time taken to calm down when upset and feeling emotionally numb or shut down) were high across the four studies regardless of gender and/or sex. Clearly, more research is needed to establish whether gender- and/or sex-based patterns in CPTSD presentation exist, but certain hypotheses are worth consideration.

Gender roles may be relevant here too. In a review of gender as a social construct in relation to PTSD diagnosis and trauma, Street and Dardis (2018) highlighted gender role-consistent differences in the experience and expression of emotions and cognitions. Women tended to experience more self-blame, more negative beliefs about the self, others and the world and higher levels of related emotions such as helplessness, fear and shame following trauma. They argue that such experiences are consistent with dominant feminine gender roles and their correlates, such as threat-based interpretations of stressors (Street & Dardis, 2018). Of course, men and gender non-binary individuals may experience similar difficulties but express these difficulties in other (perhaps gender role-congruent) ways (Street & Dardis, 2018). Indeed, qualitative findings seem to support this, with women tending to internalise emotional pain and men tending to externalise it following complex trauma (Sigurdardottir et al., 2014). Such findings may translate to CTPSD presentation in future research, as certain DSO items may be expressed differently according to dominant gender roles.

Of course, future research may show no consistent gender- and/or sex-based patterns in CPTSD presentation. Existing research highlights individual risk factors, such as psychological resources and emotion regulation strategies, as potential DSO correlates worth consideration (Fernández-Fillol et al., 2021). Fernández-Fillol et al. highlight individual resilience and the tendency towards expression- or suppression-based emotion regulation strategies as worth further exploration.

4.5. Study limitations

Papers mostly adopted a binary approach to gender and/or sex, thereby excluding gender diverse and intersex individuals and failing to address gender diversity. Relatedly, many papers conflated sex and gender, and all bar one failed to specify how participants were asked about these constructs.

Many papers lacked ethnicity data and those that did had predominantly White samples. One paper even reduced their demographics section to percentages of ‘White’ and ‘non-White’ participants. Such language serves to centre White participants as the norm, thereby othering participants whose identities do not fit this description. Studies were also predominantly conducted with Western samples. This is important given that both geography and ethnicity may pertain to cultural narratives about trauma experiences and expression, which may have influenced findings.

Few studies reported CPTSD presentation, the inclusion of which would provide insight into gender- and sex-based expressions of trauma.

4.6. Review limitations

Review limitations include inter-rater reliability. Although inter-rater review took place at title/abstract screen and full text review, only 10% of papers were reviewed at each stage. Although deemed appropriate given the scope of the current review and number of papers, future research would ideally see a greater proportion undergo inter-rater reliability testing. Second, the inclusion of search terms such as ‘gender fluid’, ‘genderqueer’, ‘non-binary’ and ‘transgender’ may have yielded additional studies. While the current review represents progress regarding gender-inclusive terminology in a continually moving context, future research should continue to expand on this. Third, international sources of doctoral theses in the database search may also have yielded further studies, which could be considered for future research.

4.7. Future research

Gender- and sex-sensitive research should be prioritised. Findings regarding the binary approach to gender and/or sex and the conflation of these constructs suggests researchers have much room for improvement. Researchers should reflect gender and sex diversity in their samples, or at least demonstrate awareness of the diversity in these constructs.

Although not a new concept (Herman, 1992), research on CPTSD diagnoses is in its relative infancy given the recency of this official diagnostic classification. Research should continue to study the experience, development and manifestation of complex trauma to develop further insights into the impact of such experiences. Diverse samples should be studied to enable thorough examination of the intersect between identity factors such as ethnicity, sexual orientation, geography and race and the experience and expression of complex trauma. Qualitative studies would also enable rich insights into the idiosyncrasies of such experiences.

4.8. Recommendations for practice

Findings suggest that attention should be paid to gender- and sex-sensitive research, and this also applies to clinical practice. If research adopts binary approaches to gender and sex, clinicians ought to be aware of biases this may perpetuate in the understanding of complex trauma. Relatedly, clinicians ought to be aware of the potential intersect between elements of identity and complex trauma experience and expression. The findings of this review suggest there are currently no consistent gender and/or sex differences in CPTSD diagnosis rates and further research is needed regarding CPTSD presentation. Findings may be shaped by societal narratives regarding gender roles and the experience and expression of complex trauma depending on elements of individuals’ identities. This is not to suggest that similarities/differences in CPTSD diagnosis rates should be overlooked or ignored. Rather, clinicians should hold both the prevalence and presentation data alongside an awareness of gender and/or sex-based scripts that may shape or influence them.

5. Conclusions

This was the first known paper to systematically review and synthesise literature on gender, sex and CPTSD to examine whether gender and/or sex differences exist in the prevalence and clinical presentation of this diagnosis. Findings were mixed. Most studies did not report in gender- and/or sex-sensitive ways. Most studies reported no gender and/or sex differences in prevalence rates. More research on CPTSD presentation is needed. Gender- and sex-sensitive research and clinical practice is needed. Awareness, both in research and clinical practice, is recommended regarding the intersect between identity and the experience and expression of complex trauma.

Appendices.

Appendix 1. Excluded papers with reasons

Study excluded	Reason for exclusion
Barnett, S. D., Hickling, E. J., & Sheppard, S. (2018). The impact of gender on the factor structure of PTSD symptoms among active-duty United States military personnel. European Journal of Trauma & Dissociation, 2, 117–124. https://doi.org/10.1016/j.ejtd.2018.01.002	No use of accepted measure
Carthy, N., Best, D., Heckels, V., Weber, L., & Eberhardt, J. (2023). Complex posttraumatic stress disorder symptoms among midlife to older female survivors of intimate partner violence. Psychological Trauma: Theory, Research, Practice and Policy, 15(2), 331–339. https://doi.org/10.1037/tra0001238	No diagnosis of CPTSD or DESNOS
Carmassi, C., Corsi, M., Bertelloni, A., Carpita, B., Gesi, C., Pedrinelli, V., Massimetti, G., Peroni, D. G., Bonuccelli, A., Orsini, A., & Dell’Osso, L. (2018). Mothers and fathers of children with epilepsy: gender differences in post-traumatic stress symptoms and correlations with mood spectrum symptoms. Neuropsychiatric Disease and Treatment, 1371–1379. https://doi.org/10.2147/NDT.S158249	No use of accepted measure
Chaplo, S. D., Kerig, P. K., Modrowski, C. A., & Bennett, D. C. (2017). Gender differences in the associations among sexual abuse, posttraumatic stress symptoms and delinquent behaviours in a sample of detained adolescents. Journal of Child & Adolescent Trauma, 10, 29–39. https://doi.org/10.1007/s40653-016-0122-z	No use of accepted measure
Craig, C. D., & Sprang, G. (2014). Gender differences in trauma treatment: do boys and girls respond to evidence-based interventions in the same way? Violence and Victims, 29(6), 927–939. https://doi.org/10.1891/0886-6708.VV-D-13-00016	No use of accepted measure
Cyr, G., Godbout, N., Cloitre, M., & Bélanger, C. (2022). Distinguishing among symptoms of posttraumatic stress disorder, complex posttraumatic stress disorder and borderline personality disorder in a community sample of women. Journal of Traumatic Stress, 35, 186–196. https://doi.org/10.1002/jts.22719	CPTSD presentation not specifically and clearly discussed
Eidhof, M. B., Djelantik, M. J., Klaassens, E. R., Kantor, V., Rittmansberger, D., Sleijpen, M., Steenbakkers, A., Weindl, D., & ter Heide, F. J. J. (2019). Complex posttraumatic stress disorder in patients exposed to emotional neglect and traumatic events: latent class analysis. Journal of Traumatic Stress, 32, 23–31. https://doi.org/10.1002/jts.22363	No use of accepted measure
Ford, J. D., Schneeberger, A. R., Komarovskaya, I., Muenzenmaier, K., Castille, D., Opler, L. A., & Link, B. (2017). The Symptoms of Trauma Scale (SOTS): psychometric evaluation and gender differences with adults diagnosed with serious mental illness. Journal of Trauma & Dissociation, 18(4), 559–574. https://doi.org/10.1080/15299732.2016.1241850	No use of accepted measure
Fox, R. (2020). An evaluation of the structure, comorbidity and correlates of posttraumatic stress responses in older adults across multiple national samples. PhD thesis, National University of Ireland.	No use of accepted measure
Gasior, K., & Chodkiewicz, J. (2020). Adverse childhood experiences in women with externalisation and internalisation disorders. Current Issues in Personality Psychology, 8(2), 119–130. https://doi.org/10.5114/CIPP.2020.96087	No use of accepted measure
Hérbert, M., Paradis, A., & Fortin, A. (2021). Symptom patterns of sexually abused teenage girls seeking services. American Journal of Orthopsychiatry, 91(4), 464–476. https://doi.org/10.1037/ort0000548	No use of accepted measure
Hopper, E. K., & Gonzalez, L. D. (2018). A comparison of psychological symptoms in survivors of sex and labor trafficking. Behavioral Medicine, 44(3), 177–188. https://doi.org/10.1080/08964289.2018.1432551	No use of accepted measure
Knefel, M., & Leuger-Schuster, B. (2013). An evaluation of ICD-11 PTSD and complex PTSD criteria in a sample of adult survivors of childhood institutional abuse. European Journal of Psychotraumatology, 4(1). https://doi.org/10.3402/ejpt.v4i0.22608	No use of accepted measure
Matthews, K. M. (2020). Exploring the lived experiences of female trauma survivors with comorbid substance use disorder. PhD thesis, University of Mississippi.	No diagnosis of CPTSD or DESNOS
McGinty, G., Fox, R., & Hyland, P. (2023). Assessing prevalence, validity and correlates of ICD-11 posttraumatic stress disorder and complex posttraumatic stress disorder in Ireland. Psychological Trauma: Theory, Research, Practice and Policy. https://doi.org/10.1037/tra0001472	CPTSD not separated by gender
Milne, L., Collin-Vézina, D., & Wekerle, C. (2021). Diverse trauma profiles of youth in group care settings: a cluster analysis. Child Abuse & Neglect, 120. https://doi.org/10.1016/j.chiabu.2021.105221	No use of accepted measure
Nutskova, E. V. (2016). Phenomenology of the psychological consequences of sexual abuse in children and adolescents depending on the action of various factors. Psychology and Law, 6(1), 73–90. https://doi.org/10.17759/psylaw.2016060107	No use of accepted measure
Polusny, M. A., Kumpula, M. J., Meis, L. A., Erbes, C. R., Arbisi, P. A., Murdoch, M., Thuras, P., Kehle-Forbes, S. M., & Johnson, A. K. (2014). Gender differences in the effects of deployment-related stressors and pre-deployment risk factors on the development of PTSD symptoms in National Guard soldiers deployed to Iraq and Afghanistan. Journal of Psychiatric Research, 49, 1–9. https://doi.org/10.1016/j.jpsychires.2013.09.016	No use of accepted measure
Post, M., Hanten, G., Li, X., Schmidt, A. T., Avci, G., Wilde, E. A., & McCauley, S. R. (2014). Dimensions of trauma and specific symptoms of complex posttraumatic stress disorder in inner-city youth: a preliminary study. Violence and Victims, 29(2), 262–279. https://doi.org/10.1891/0886-6708.VV-D-12-00097R1	No use of accepted measure
Powers, A., Fani, N., Carter, S., Cross, D., Cloitre, M., & Bradley, B. (2017). Differential predictors of DSM-5 PTSD and ICD-11 complex PTSD among African American women. European Journal of Psychotraumatology, 8(1). https://doi.org/10.1080/20008198.2017.1338914	CPTSD presentation not specifically and clearly discussed
Sigurdardottir, S., Halldorsdottir, S., & Bender, S. S. (2014). Consequences of childhood sexual abuse for health and well-being: Gender similarities and differences. Scandinavian Journal of Public Health, 42, 278–286. https://doi.org/10.1177/1403494813514645	No diagnosis of CPTSD or DESNOS
Smith, J. A., Zhang, J., Urusov, A., Colucci, L., Sloss, I., Eckert, L., Price-Cameron, M., & Browne, D. T. (2023). Exploring gender differences in complex developmental trauma symptomatology among children and adolescents involved in child welfare. https://doi.org/10.31234/osf.io/5qtu6	No use of accepted measure
Taha, P. H., & Sijbrandij, M. (2021). Gender differences in traumatic experiences, PTSD and relevant symptoms among the Iraqi internally displaced persons. International Journal of Environmental Research and Public Health, 18. https://doi.org/10.3390/ijerph18189779	No use of accepted measure
Wamser-Nanney, R., & Cherry, K. E. (2018). Children’s trauma-related symptoms following complex trauma exposure: evidence of gender differences. Child Abuse & Neglect, 77, 188–197. https://doi.org/10.1016/j.chiabu.2018.01.009	No use of accepted measure

Appendix 2. Included papers

Study included
Charak, R., Cano-Gonzalez, I., Tirado, R. R., Ford, J. D., Byllesby, B. M., Shevlin, M., Karatzias, T., Hyland, P., & Cloitre, M. (2023). Factor structure of the International Trauma Questionnaire in trauma exposed LGBTQ + adults: role of accumulating traumatic events and minority stress heterosexist experiences. Psychological Trauma: Theory, Research, Practice and Policy, 15(4), 628–636. https://doi.org/10.1037/tra0001440
Cloitre, M., Hyland, P., Bisson, J. I., Brewin, C. R., Roberts, N. P., Karatzias, T., & Shevlin, M. (2019). ICD-11 posttraumatic stress disorder and complex posttraumatic stress disorder in the United States: a population-based study. Journal of Traumatic Stress, 32(6), 833–842. https://doi.org/10.1002/jts.22454
de Vries, S., Juhnke, G. A., & Keene, C. T. (2018). PTSD, complex PTSD and childhood abuse: gender differences among a homeless sample. Journal for Social Action in Counseling and Psychology, 10(2). https://doi.org/10.33043/JSACP.10.2.2-15
Fernández-Fillol, C., Pitsiakou, C., Perez-Garcia, M., Teva, I., & Hidalgo-Ruzzante, N. (2021). Complex PTSD in survivors of intimate partner violence: risk factors related to symptoms and diagnoses. European Journal of Psychotraumatology, 12(1), 2003616. https://doi.org/10.1080/20008198.2021.2003616
Giarratano, P., Ford, J. D., & Nochajski, T. H. (2020). Gender differences in complex posttraumatic stress symptoms, and their relationship to mental health and substance abuse outcomes in incarcerated adults. Journal of Interpersonal Violence, 35(5–6), 1133–1157. https://doi.org/10.1177/0886260517692995
Gilbar, O., Hyland, P., Cloitre, M., & Dekel, R. (2018). ICD-11 complex PTSD among Israeli male perpetrators of intimate partner violence: construct validity and risk factors. Journal of Anxiety Disorders, 54, 49–56. https://doi.org/10.1016/j.janxdis.2018.01.004
Hecker, T., Huber, S., Maier, T., & Maercker, A. (2018). Differential associations among PTSD and complex PTSD symptoms and traumatic experiences and postmigration difficulties in a culturally diverse refugee sample. Journal of Traumatic Stress, 31, 795–804. https://doi.org/10.1002/jts.22342
Ho, G. W. K., Hyland, P., Karatzias, T., Bressington, D., & Shevlin, M. (2021). Traumatic life events as risk factors for psychosis and ICD-11 complex PTSD: a gender-specific examination. European Journal of Psychotraumatology, 12(1), 2009271. https://doi.org/10.1080/20008198.2021.2009271
Hyland, P., Ceannt, R., Daccache, F., Abou Daher, R., Sleiman, J., Gilmore, B., Byrne, S., Shevlin, M., Murphy, J., & Vallières, F. (2018). Are posttraumatic stress disorder (PTSD) and complex-PTSD distinguishable within a treatment-seeking sample of Syrian refugees living in Lebanon? Global Mental Health, 5, e14. https://doi.org/10.1017/gmh.2018.2
Karatzias, T., Hyland, P., Bradley, A., Cloitre, M., Roberts, N. P., Bisson, J. I., & Shevlin, M. (2019). Risk factors and comorbidity of ICD-11 PTSD and complex PTSD: findings from a trauma-exposed population based sample of adults in the United Kingdom. Depression and Anxiety, 36(9), 887–894. https://doi.org/10.1002/da.22934
McGinty, G., Fox, R., Ben-Ezra, M., Cloitre, M., Karatzias, T., Shevlin, M., Hyland, P. (2021). Sex and age differences in ICD-11 PTSD and complex PTSD: an analysis of four general population samples. European Psychiatry, 61(1), 1–9. https://doi.org/10.1192/j.eurpsy.2021.2239
Søegaard, E. G. I., Kan, Z., Koirala, R., Hauff, E., & Thapa, S. B. (2021). Gender differences in a wide range of trauma symptoms after victimization and accidental traumas: a cross-sectional study in a clinical setting. European Journal of Psychotraumatology, 12(1), 1975952. https://doi.org/10.1080/20008198.2021.1975952

Appendix 3. MMAT quality assessment descriptive summary

Criterion
Study	4.1. Sampling strategy relevant to research question?	4.2. Sample representative of target population?	4.3. Appropriate measurements?	4.4. Low risk of nonresponse bias?	4.5. Appropriate statistical analysis to answer research question?
Charak et al. (2023)	Social media and LGBTQ + associations and influencers contacted to recruit LGBTQ + Ps. Relevant and appropriate for research question. 1	Target population seems to be Spain. No reference to sample representativeness. 0	LEC; ITQ Spanish version. Valid and reliable. 1	No reference to non-response rate. 0	Statistics described and appropriate. 1
Cloitre et al. (2019)	Probability sampling (from nationally representative community sample) to randomly recruit Ps with experience of 1 + traumatic event. 1	National representative online community sample + statistics to ensure representative of adult U.S. population aged 18–70. 1	ITQ; LEC. Appropriate, valid, reliable. 1	Participation rate 46.3%. No reference to reasons for nonresponse or statistical corrections. 0	Statistics for each hypothesis described and appropriate. 1
de Vries et al. (2018)	Non-random sampling – Ps were recruited in homeless shelters. Appropriate for target population. 1	Target population not clear and no reference to sample representativeness. 0	SIDES; Trauma Centre PTSD Scale. Both valid and reliable. 1	No reference to non-response rate. 0	Statistics reported in results, but no reference in methods section to statistical analysis used. 0
Fernández-Fillol et al. (2021)	Non-random sampling – Ps who had experienced IPV recruited in associations and women’s centres. Appropriate for target population. 1	Assumed target population women who had experienced IPV across Spain, but not explicitly stated. 0	ITQ Spanish version validated for use with this population. 1	All except one P approached participated. Reason for non-participation stated. 1	Statistical analyses described and appropriate. 1
Giarratano et al. (2020)	Random sampling of all new admissions to all relevant prisons across state. Sample relevant to target population. 1	Target population stated (incarcerated adults) and reference to sample representativeness. 1	SIDES; SCID; TEI. All appropriate, valid, reliable. 1	Proportion of nonresponses stated and relatively low (7%), and reasons stated (refusal). 1	Statistical analyses described and appropriate. 1
Gilbar et al. (2018)	Random sampling from target population. 1	Target population stated (Israeli male perpetrators of IPV) but no reference to sample representativeness. 0	ITQ; LEC-5. No reference to versions used or psychometrics among Israeli individuals. 0	Proportion of nonresponses inferred (70% completion). No reasons given or reference to statistical compensation. 0	Statistical analyses described and appropriate. 1
Hecker et al. (2018)	Non-random sampling of refugees and asylum seekers in counselling and information centres. Appropriate strategy for, and sample relevant to, target population. 1	Target population stated (asylum seekers and refugees resettled in Switzerland) and reference to sample representativeness. 1	HTQ; ITQ. Both valid and reliable. Translated from English and back translated to English by trained translators. 1	Low proportion of nonresponses (4.1%) and reasons stated. 1	Statistical analyses described and appropriate. 1
Ho et al. (2021)	Non-random sample from existing internet research panels to generate nationally representative sample of Irish adults. Appropriate for research question. 1	Target population stated (Ireland) and reference to sample representativeness. 1	ITEM; ITQ. Validated in target population and appropriate. 1	No reference to nonresponse rate. 0	Statistical analyses described and appropriate. 1
Hyland, Ceannt, et al. (2018)	Non-random sampling of treatment-seeking Syrian refugees living in Lebanon – appropriate to target population. 1	Target population stated (treatment-seeking Syrian refugees living in Lebanon) but no reference to sample representativeness. 0	ITQ-Arabic version. Validated for use with Arabic-speaking individuals. Appropriate. 1	No reference to nonresponse rate. 0	Statistical analyses described and appropriate. 1
Karatzias et al. (2019)	Random sampling of trauma-exposed adults from existing online research panel representative of UK population. Appropriate for research question. 1	Target population stated (UK adults) and reference to sample representativeness. 1	LEC-5; ITQ. Appropriate, valid, reliable. 1	All randomly selected Ps who met inclusion criteria participated. 1	Statistical analyses described and appropriate. 1
McGinty et al. (2021)	Four samples (UK, USA, Ireland, Israel) – data non-randomly selected from nationally representative (bar UK) samples of pre-existing data. Appropriate for research question. 1	Target populations stated and reference to sample representativeness. 1	LEC-5 for UK, USA, Israel samples; ITEM for Irish sample; ITQ. No reference to version of ITQ used. 0	No reference to nonresponse rate. 0	Statistical analyses described and appropriate. 1
Søegaard et al. (2021)	Non-random sample of severely traumatised individuals attending outpatient clinic. Appropriate for research question. 1	Target population not clear and no reference to sample representativeness. 0	LEC; SCI-1-PTSD; SIDES. No reference to psychometrics among Norwegian individuals. 0	Relatively low nonresponse (nine out of 119; 7.6%) due to consent withdrawal. 1	Statistical analyses described and appropriate. 1

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data sharing is not applicable to this article as no new data were created or analysed in this study.