Table 3.

Characteristics of the studies: The following are studies that report any factors associated or not associated with treatment outcome of psychological therapies of PTSD.

Study	Country	Intervention	Participants	Type of trauma	Factors associated (or not) with treatment outcome
(Basoglu et al., 2005)	Turkey	Single-session CBT	59	Earthquake	Greater PTSD severity, higher education and past trauma had no significant association with treatment outcome as measured by the CAPS-IV but it was associated with less improvement in the Patients Global Impression (a self-measure that reflect a patient’s belief about efficacy of treatment).
(Basoglu et al., 2007)	Turkey	Single-session CBT	31	Earthquake	Age, gender, education, past psychiatric illness, history of past trauma, time since the earthquake, and the pre-treatment clinical ratings were not significantly associated with treatment outcome.
(Blanchard et al., 2003)	USA	Trauma focused CBT	98	Road Traffic accidents	There was no main effect or interaction with therapist gender or no main effect of gender of patient to treatment outcome.
(Cloitre et al., 2002)	USA	CBT-T	58	Various	Predictors of improvement were therapeutic alliance and improvement in Negative mood regulation as measured by the NMR as measured by the CAPS. Significant reduction posttreatment in depression and anxiety were not associated with PTSD symptom severity reduction.
(Cloitre et al., 2016)	USA	Skills training in affective and interpersonal regulation (STAIR) followed by Prolonged Exposure (EXP)	104	Childhood sexual and physical trauma/abuse	Higher emotional regulation predicted better functioning. Those with high ‘Symptom burden’ (PTSD, depression, dissociation and interpersonal problems) was associated with worse treatment outcome, and did least well in exposure, moderately well in skills and best in the combination as measured by the PTSD symptom severity, assessed via the CAPS.
(Dorrepaal et al., 2012)	Netherlands	Stabilizing Group Treatment	71	Child Abuse	Diagnosis of Borderline Personality Disorder (BPD) was associated with greater compliance, defined by completed treatment, as opposed to those without the personality diagnosis.
(Ehlers et al., 2003	UK	Cognitive Therapy (CT)	85	Road Traffic accident	Neither time since trauma nor the degree of change in PTSD severity (PDS) score with self-monitoring were associated with outcome.
(Fonzo et al., 2017)	USA	Prolonged Exposure (PE)	66	Not specified	Less Blood Oxygen Level Dependent activation (signal) in the brain at baseline was associated with greater reductions in symptom scores in the waiting list group in two right and two left dorsolateral prefrontal clusters. Finally, greater dorsal anterior cingulate activation at baseline was associated with greater reductions in symptom scores in the treatment group but not in the waiting list group
(Galovski et al., 2012)	USA	Modified Cognitive Processing Therapy (M-CPT)	100	Various	Treatment dropouts were younger, had fewer years of education and had lower annual household income and significantly higher pre-treatment CAPS severity at baseline assessment. Participant age, time since index trauma and pre-treatment CAPS and Beck Depression Inventory-II scores were identified as potential predictors of length of therapy.
(Haagen et al., 2017)	Netherlands	Eye Movement Desensitization and Reconsolidation and Stabilization (EMDR-S).	72	Various	Patients with severe levels of depression at baseline as measured by The Hopkins Symptom Checklist had progressively less PTSD symptom reduction over time. A diagnosis of major depressive disorder was predictive of poor treatment response, indicating that patients with a major depressive disorder improved less than patients without a major depressive disorder. None of the other predictors (pre-treatment PTSD severity, refugee status, interpreter presence during therapy, the number and nature of traumatic events, gender, number of psychotherapy sessions, and treatment dropout) were significantly associated with treatment outcome.
(Hien et al., 2017)	USA	Concurrent Treatment of PTSD and SUD using Prolonged Exposure (COPE).	110	Various	Baseline emotional dysregulation (ED) severity moderated treatment outcomes such that high ED was associated with greater reduction in PTSD severity among those who received COPE relative to RPT and AMCG. In contrast, low ED as association with greater reduction in substance use among those in RPT relative in COPE and AMCG.
(Ivarsson et al., 2014)	Sweden	Guided Internet Delivered Cognitive Behaviour Therapy for PTSD.	62	Various	Participant lost to follow-up were on average younger compared to those who completed the study. Gender, age, marital status, highest educational level, unemployment status, psychopharmacological medication and history of psychotherapy were not associated with treatment outcome.
(Karatzias et al., 2007)	UK	Eye Movement Desensitisation and Repro- cessing (EMDR) vs Imaginal Exposure and Cognitive Restructuring (E+ CR)	48	Various	Higher pre- to post-treatment CAPS total change score was significantly associated with fewer sessions and a lower baseline CAPS total score. Age, gender, marital status, occupation, type of trauma, time since trauma, therapy type, number of sessions, psychotropic medication, CAPS total (baseline), HADS-A, HADS-Dwere not associated with treatment outcome, as measured by pre and post CAPS severity scores.
(Krakow et al., 2000)	USA	Imagery Rehearsal Therapy (IRT)	169	Sexual assault	Demographic covariates; ethnicity, marital status, annual income, or education were not significant in any of the analyses.
(Kubany et al., 2004)	USA	Cognitive Trauma Therapy for Battered Women (CTT-BW)	125	Domestic Abuse	Comorbidity with depression, low self-esteem, younger age, less educated, and more shame prone at the initial assessment were associated with non-completers of treatment.
(Lewis et al., 2017)	UK	Internet-based guided self-help	42	Various	There was no significant effect modification by age, gender, baseline CAPS score, number of modules completed, or number of therapist minutes. However, more recent trauma experienced a slightly improved effect. Higher education was associated with greatest treatment effect, and those with a higher degree experiencing greater improvement in CAPS scores.
(Marks et al., 1998)	UK	Prolonged Exposure (PE) Vs Cognitive restructuring	87	Various	Adherence to homework was associated with more improvement on the Global Improvement scale.
(McDonagh et al., 2005; Possemato et al., 2016)	USA	Primary Care Brief Mindfulness Training (PCBMT) Cognitive Behavioural Therapy (CBT)	6274	Military Trauma Child Sexual Abuse	The ability to describe internal experiences, thoughts emotions and sensations, in non-judgemental way was associated with decrease in PTSD symptoms. Participants who dropped out of CBT endorsed more depression and greater anxiety, reported lower quality of life, and endorsed more distorted schemas on The Traumatic Stress Institute Beliefs Scale (TSI; Pearlman, 2001) than those who stayed in treatment.
(Possemato et al., 2016; Schnurr et al., 2003)	USA	Trauma-focused Group Psychotherapy Primary Care Brief Mindfulness Training (PCBMT)	36,062	Military Trauma	Individuals who were lost to follow-up had lower Global Assessment of Functioning scores, were more likely to be unemployed and have a lifetime history of substance abuse or dependence. The ability to describe internal experiences, thoughts emotions and sensations, in non-judgemental way was associated with decrease in PTSD symptoms.
(Schnurr et al., 2007; Schnurr et al., 2003)	USA	Prolonged Exposure (PE) vs Present-centred therapy (PCT). Trauma-focused Group Psychotherapy	277,360	Female Veterans Military Trauma	Participants in Present Centred Therapy received an increase or new medication during the study compared to those in the prolonged exposure group. Exploratory analyses to determine whether medication change during treatment modified the treatment effect for CAPS severity scores indicated that the interaction between medication change and treatment was not significant. Individuals who were lost to follow-up had lower Global Assessment of Functioning scores, were more likely to be unemployed and have a lifetime history of substance abuse or dependence.
(Schnurr et al., 2007; Spence et al., 2011)	USA	Internet delivered Cognitive Behavioural Therapy (I-CBT) for PTSD. Prolonged Exposure (PE) vs Present-centred therapy (PCT).	125,277	Various Female Veterans	There was no significant relationship between post-treatment outcome the amount of time spent on the homework or with the amount of time spent on thought challenging. Participants in Present Centred Therapy received an increase or new medication during the study compared to those in the prolonged exposure group. Exploratory analyses to determine whether medication change during treatment modified the treatment effect for CAPS severity scores indicated that the interaction between medication change and treatment was not significant.
(Spence et al., 2011; Stirman et al., 2018)	USA	Cognitive Processing Therapy (CPT). Internet delivered Cognitive Behavioural Therapy (I-CBT) for PTSD.	140,125	Sexual or physical violence Various	Completing homework was associated with a greater decrease in PTSD symptom severity score, as measured by the PTSD symptom scale (PSS). There was no significant relationship between post-treatment outcome the amount of time spent on the homework or with the amount of time spent on thought challenging.
(Stapleton et al., 2006; Stirman et al., 2018)	USA	Prolonged Exposure (PE)Cognitive Processing Therapy (CPT).	60,140	Various Sexual or physical violence	No evidence that treatment outcome varied as a function of the pre-treatment severity of anger or guilt. Additional presence of stressors had no associated with treatment outcome. Completing homework was associated with a greater decrease in PTSD symptom severity score, as measured by the PTSD symptom scale (PSS).
(Stapleton et al., 2006; Wilson et al., 1995)	USA	Eye Movement Desensitization and Reprocessing (EMDR) Prolonged Exposure (PE)	8060	Various	PTSD-I scale symptom severity at baseline, years of education, income, gender, gender of therapist were not associated with treatment outcome. Participants who were married were associated with greater gain. No evidence that treatment outcome varied as a function of the pre-treatment severity of anger or guilt. Additional presence of stressors had no associated with treatment outcome.
(Wilson et al., 1995)	USA	Eye Movement Desensitization and Reprocessing (EMDR)	80	Various	PTSD-I scale symptom severity at baseline, years of education, income, gender, gender of therapist were not associated with treatment outcome. Participants who were married were associated with greater gain.