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. Author manuscript; available in PMC: 2022 Apr 1.
Published in final edited form as: Addict Behav. 2021 Jan 5;115:106793. doi: 10.1016/j.addbeh.2020.106793

A GENDER COMPARATIVE ANALYSIS OF POST-TRAUMATIC STRESS DISORDER AMONG A COMMUNITY-BASED COHORT OF PEOPLE WHO USE DRUGS IN VANCOUVER, CANADA

Sanjana Mitra a,b, William Lee b, Kanna Hayashi b,c, Jade Boyd b,d, MJ Milloy b,d, Huiru Dong b,e, Evan Wood b,d, Thomas Kerr b,d,*
PMCID: PMC7971763  NIHMSID: NIHMS1677675  PMID: 33421746

Abstract

Background:

While exposure to traumatic events and subsequent post-traumatic stress disorder (PTSD) are common among people who use drugs (PWUD), little is known about gender-based differences associated with PTSD in this population. We explore gender-based differences in factors associated with a probable PTSD diagnosis in a cohort of PWUD from Vancouver, Canada.

Methods:

Data were collected through the Vancouver Injection Drug Users Study (VIDUS) and the AIDS Care Cohort to Evaluate Exposure to Survival Services (ACCESS), two community-recruited cohorts of PWUD. Participants were administered the PTSD Checklist for DSM-5. Multivariable logistic regression was used to investigate social-structural factors and substance use patterns and behaviours associated with a probable PTSD diagnosis, stratified by self-identified gender. PTSD symptom clusters and brief descriptions of the worst traumatic event experienced were also reported.

Results:

Between December 2016 and December 2018, of 797 eligible participants, 295 (37.0%) identified as women. PTSD was more commonly reported in women compared to men (53.2% vs. 31.5%, p<0.001). In multivariable analysis involving men, no correlates were associated with PTSD. In multivariable analysis involving women, PTSD was positively associated with exposure to violence (AOR: 3.66; 95%CI: 1.14–11.72), daily stimulant use (AOR: 2.32; 95%CI: 1.32–4.08) and heavy alcohol use (AOR: 3.84; 95%CI: 1.84–8.00), and negatively associated with being in a stable relationship (AOR: 0.46; 95%CI: 0.25–0.84).

Conclusions:

Gender-based differences in PTSD diagnosis among a cohort of PWUD point to the need to develop gender-focused and trauma-informed health and social services to meet the immediate needs of PWUD living with PTSD.

Keywords: Post-traumatic stress disorder, people who use drugs, substance use disorder, gender difference, trauma-informed care

1.0. INTRODUCTION

Traumatic events have severe consequences for people who use drugs (PWUD) (Peirce, Brooner, King, & Kidorf, 2016). Research indicates a high prevalence of lifetime exposure to traumatic events among PWUD, with approximately one-in-four individuals subsequently meeting diagnostic criteria for PTSD (Peirce, Brooner, Kolodner, Schacht, & Kidorf, 2013). Epidemiological studies indicate a high prevalence of PTSD among substance-using populations compared to the general population, with lifetime and current rates of PTSD ranging from 30–50% and 20–39% among people with substance use disorders (SUD), and corresponding rates in the general population ranging from 7–9% and 2–4% (Kessler, Berglund, et al., 2005; Kessler, Chiu, Demler, Merikangas, & Walters, 2005; Najavits et al., 1998; Reynolds et al., 2005; Triffleman, Marmar, Delucchi, & Ronfeldt, 1995; Van Ameringen, Mancini, Patterson, & Boyle, 2008).

The health and psycho-social consequences associated with the co-occurring conditions are wide ranging. Intrusive thoughts and impulsivity associated with trauma and PTSD may lead to maladaptive coping behaviours and worsened health outcomes (Lee et al., 2019). Symptoms include greater impaired functioning, higher rates of co-morbid psychiatric disorders and increased likelihood of relapse following SUD treatment (Lee et al., 2019; Reynolds et al., 2005; Sullivan et al., 2016; Weiss, Tull, Viana, Anestis, & Gratz, 2012). Furthermore, a Canadian study involving a cohort of PWUD found that those with a probable PTSD diagnosis had a two-fold higher odds of experiencing non-fatal overdose compared to those without PTSD (Lee et al., 2019), shedding light on the overlap between psycho-social factors and drug-related harm (Kerr, 2019; Lee et al., 2019).

The leading theory explaining co-occurring PTSD and SUD is the theory of self-medication, which posits that individuals who experience traumatic events may develop PTSD and use substances to reduce re-experiencing trauma and manage symptoms (Khantzian, 1985). This theory is supported by evidence indicating that PTSD typically emerges before SUD (Kessler, Demler, et al., 2005; Ouimette, Read, Wade, & Tirone, 2010) and research suggesting that the primary rationale of substance use in individuals with co-occurring disorders is the management of PTSD symptoms, where symptom severity has been shown to predict drug cravings and drug preferences reflect symptom cluster severity (Flanagan, Korte, Killeen, & Back, 2016; Khantzian, 1985; Lee et al., 2019; Leeies, Pagura, Sareen, & Bolton, 2010; Logrip, Zorrilla, & Koob, 2012). Additional research suggests that early life stressors and social-structural adversities further accelerate neurological and physiological dysregulation, exacting their toll on coping mechanisms and affecting the disorder’s trajectory (Nurius, Uehara, & Zatzick, 2013).

Gender-based differences in PTSD development are well established. While traumatic events are more common in men, women are two-to-three times more likely to develop PTSD (Olff, 2017). Numerous explanations of women’s unique susceptibility to PTSD have been identified, including greater fear conditioning and heightened response to stress in women compared to men, as well as gender-based differences coping mechanisms (Inslicht et al., 2013; Najavits, Weiss, & Shaw, 1997; Olff, 2017). Women more frequently report defensive and palliative coping which may worsen psychological distress, whereas men more commonly report problem-focused coping mechanisms (Olff, 2017). Females likewise appear to have a more sensitized hypothalamic-pituitary-adrenal axis compared to males, further contributing to women’s increased risk of developing PTSD (Olff, 2017).

Despite a well-established understanding of the association between PTSD and SUD and gender-based differences in PTSD development, less is understood about gender differences between trauma and PTSD among people with longstanding histories of drug use. Ethnographic research in Vancouver, Canada’s Downtown Eastside – a neighborhood characterized by a longstanding history of criminalization and poverty, as well as drug-user activism, has highlighted how structural and everyday gender-based violence impacts women who use drugs (J. Boyd et al., 2018; Collins et al., 2018; McNeil, Shannon, Shaver, Kerr, & Small, 2014). Structural violence (i.e. violence embedded within social structures and institutional processes) and everyday violence (i.e. day-to-day threats of physical and sexual assault) operate to perpetuate and normalize violence experienced by women who use drugs (Bourgois, Prince, & Moss, 2004; J. Boyd et al., 2018; Collins et al., 2018; McNeil et al., 2014; Pinkham, Stoicescu, & Myers, 2012; Rhodes et al., 2012; Scheper-Hughes, 1996). These forms of violence often have a direct effect on a woman’s ability to negotiate drug use and safer sex practices, shaping drug-related harm (J. Boyd et al., 2018; Collins et al., 2018; McNeil et al., 2014; Pinkham et al., 2012). Gender-based differences in types of trauma experienced by women and men who use drugs may also shape women’s increased susceptibility of re-victimization and subsequent development of PTSD (Marshall, Fairbairn, Li, Wood, & Kerr, 2008; Plotzker, Metzger, & Holmes, 2007; Schumm, Hobfoll, & Keogh, 2004; Sullivan et al., 2016; Ullman, Relyea, Peter-Hagene, & Vasquez, 2013).

With regards to co-occurring PTSD and substance use trajectories, women with experiences of trauma have a more rapid onset of substance use compared to women who have not experienced trauma (Najavits et al., 1997). Women with PTSD have also been shown to demonstrate higher intensity drug and alcohol use behaviours compared to women without the disorder (Sullivan et al., 2016). In additional support of the self-medication hypothesis and the evidence above (Najavits et al., 1997), other research indicates the prevalence of co-occurring PTSD and SUD is greater in women compared to men, and that compared to men, women are more likely to use substances to cope with the effects of trauma and stress (Back, Sonne, Killeen, Dansky, & Brady, 2003; Lehavot et al., 2018).

Although some studies have characterized gender-based violence among PWUD, less is understood about the gender-based differences in concomitant experiences of PTSD in this population. While some studies have examined PTSD in relation to substance use separately among men and women, as well across heterogeneous populations (Lopez-Castro, Hu, Papini, Ruglass, & Hien, 2015; Plotzker et al., 2007; Schumm et al., 2004; Sullivan et al., 2016; Ullman et al., 2013), few gender-comparative studies examining PTSD differences among individuals with histories of drug use exist (Cottler, Nishith, & Compton, 2001; Johnson, Heffner, Blom, & Anthenelli, 2010). Moreover, despite increased interest in addressing comorbid PTSD and SUD in recent years, less is known about the gendered socio-structural contexts and substance use-specific differences among PWUD with elevated rates of trauma. Accordingly, we sought to conduct a gender-stratified analysis of probable PTSD diagnosis among men and women in two community-based cohorts of PWUD from Vancouver, Canada. The objectives of this study were to: 1) determine the prevalence of PTSD diagnosis among women and men who use drugs in this cohort and 2) characterize gender-based differences in socio-structural factors and drug use patterns and behaviours associated with PTSD diagnosis. Given the high rates of past and recurrent trauma and violence experienced by this population (Marshall et al., 2008; Peirce et al., 2013), the broader exploration of gendered differences in PTSD holds potential to inform trauma-informed and gender-focused programming and policies to support the immediate needs of PWUD with histories of trauma.

2.0. MATERIAL AND METHODS

2.1. Study Participants and Design

This study draws on the Vancouver Injection Drug Users Study (VIDUS) and the AIDS Care Cohort to Evaluate exposure to Survival Services (ACCESS). Participants are continually recruited through self-referral and community outreach from the Downtown Eastside. The VIDUS cohort includes HIV-seronegative adults who injected drugs in the last month before study enrolment. The ACCESS cohort includes HIV-seropositive adults who used drugs other than cannabis in the last month before study enrolment (Wood et al., 2009; Wood, Stoltz, Montaner, & Kerr, 2006).

The cohorts use harmonized procedures, allowing for combined analysis of study participants (Hayashi et al., 2018). At baseline and semiannual follow-ups, participants answered a structured interviewer-administered questionnaire obtaining detailed data on demographics, socio-structural exposures, and substance use behaviours and health-related outcomes. Participants provided written informed consent and received an honorarium of $40 for each visit. Ethics approval was obtained from the University of British Columbia and Providence Health Care Research Ethics Boards. Participants for the current study were asked to answer a supplemental questionnaire that assessed for the Diagnostic and Statistical Manual of Mental Disorders PTSD Symptomology (i.e. the PTSD Checklist for DSM-5 – (PCL-5)). Participants further provided informed consent and were compensated an additional $15.

2.2. Measures

This study includes participants who were enrolled in the VIDUS and ACCESS cohorts between December 2016 and December 2018 and completed the PCL-5. The PCL-5 is a 20-item self-reported measure that assesses DSM-5 symptoms of PTSD in the past 30 days for the purposes of making a probable diagnoses (Weathers, 2013). The rating scale for each symptom consists of a five-point Likert scale ranging from zero to four and corresponds respectively to “not at all”, “a little bit”, “moderately”, “quite a bit” and “extremely”. Symptom clusters measured include Cluster B: intrusive symptoms (item 1–5), Cluster C: avoidance symptoms (item 6–7), Cluster D: negative alterations in mood and cognition (items 8–14) and Cluster E: negative alterations in arousal and activity (items 15–20). The total symptom severity score was obtained by summing the total score for all 20 items (Bovin et al., 2016). The PCL-5 was administered by trained research interviewers with backgrounds in counseling psychology. The outcome was probable PTSD diagnosis, defined by a PCL-5 cut-point score of ≥31 versus <31. This cut-off-point was identified within a range that is optimally efficient for diagnosing PTSD (Weathers, 2013). The Cronbach’s alpha for the PTSD items was 0.96. The PCL-5 also yielded good test-retest reliability (r=0.84 reference) (Blevins, Weathers, Davis, Witte, & Domino, 2015).

Self-reported gender was categorized as woman versus man, with transgender participants grouped according to their self-reported gender identity. We reported sample characteristics by gender and examined gender-stratified correlates associated with the outcome, probable PTSD diagnosis. A range of covariates hypothesized to be associated with the outcome were considered to elucidate gender-based differences among those with PTSD to highlight opportunities to inform gender-focused programming and policies. These variables were selected based on past empirical work on trauma and substance use, as well as context-dependent knowledge (Boyd et al., 2018; Cottler et al., 2001; Najavits et al., 1997; Peirce et al., 2013). Demographic variables considered included: age (per year older), White ethnicity (White versus Non-White) and relationship status (legally married/common law/regular partner versus other). Socio-structural exposures that occurred in the past 6 month follow-up period and were considered included: experiencing any physical or sexual violence (yes versus no), experiencing homelessness (yes versus no), recent incarceration (in detention, prison or jail; yes versus no), engaging in trading sex for money, gifts, food, shelter, clothes (yes versus no), and irregular income generation (yes versus no, including illegal income [e.g. theft] and street-based income generation [e.g. recycling] and enrolment in social assistance programs). Substance use behaviours and health-related patterns that occurred in the past 6 months and were considered included: at least daily heroin use (yes versus no), at least daily stimulant use (yes versus no), binge drug use (defined as using more alcohol than usual, yes versus no), heavy alcohol use (defined according to the National Institute on Alcohol Abuse and Alcoholism (National Institute on Alcohol Abuse and Alcoholism, 2020); yes versus no), engaging in any form of unprotected sex (yes versus no), current enrollment in drug or alcohol treatment (including use of one or a combination of opioid substitution therapy, detox programs, drug court, residential drug treatment and outpatient counselling; yes versus no) and recent self-reported overdose (defined as having a negative reaction from using too many drugs or having a bad trip, yes versus no). Supplemental analyses using the aforementioned variables were conducted to estimate gender-stratified associations with symptom cluster endorsement to provide further relevant clinical information.

Participants were reported as endorsing a symptom cluster if they responded to at least experiencing one symptom rated “moderately” or more severe (≥2) for Clusters B and C, and if they responded to at least two symptoms rated “moderately” or more severe (≥2) for Clusters D and E (Weathers, 2013). As part of the PCL-5, participants completed a 17-item checklist of traumatic events that occurred through the life course. Participants were asked to describe the worst traumatic event experienced and associated with reported PTSD symptomology. Brief descriptions of the worst event were grouped into thematic categories. Data were also obtained on characteristics of the worst event.

2.3. Statistical Analyses

Baseline characteristics and self-reported gender identity were assessed through chi-square tests for categorical variables and Mann-Whitney U tests for continuous variables.

Correlates associated with PTSD diagnosis, stratified by gender were assessed. We conducted bivariable and multivariable logistic regression models with a range of key variables that were selected based on theoretical and empirical precedent, as well as previous studies on PTSD, substance use, and local knowledge of Vancouver’s Downtown Eastside (J. Boyd et al., 2018; Cottler et al., 2001; Najavits et al., 1997; Peirce et al., 2013). In supplementary analyses, using the modeling approach described above, the gender-stratified correlates associated with PTSD symptom cluster endorsement were estimated. Gender-stratified proportions of PTSD symptom clusters and brief descriptions of the worst traumatic event were reported. All p-values were two-sided and statistical analyses were preformed using SAS software version 9.4 (Cary, 2014).

3.0. RESULTS

Of 797 participants assessed for PTSD, the median age was 50.9 (interquartile range [IQR]:42.2–56.8) years, 295 (37.0%) identified as women, and 315 (39.5%) had a probable PTSD diagnosis. PTSD was more commonly reported in women compared to men (53.2% vs. 31.5%, p<0.001). Table 1 reports gender-stratified sample characteristics.

Table 1.

Baseline characteristics of participants among a cohort of PWUD in Vancouver, Canada stratified by gender (N= 797).

Gender
Characteristic Men N=502 (63.0)
n (%)		 Women N=295 (37.0)
n (%)		 p-value
PTSD diagnosisa (≥ 31)
Yes 158 (31.5) 157 (53.2) <0.001
No 344 (68.5) 138 (46.8)
Median age (IQR) 52.8 (45.6–58.0) 46.5 (37.9–53.3) <0.001
Ethnicity
White 244 (48.7) 89 (30.2) <0.001
Non-White 257 (51.3) 206 (69.8)
Relationship status
Legally married/common law/regular partner 121 (24.2) 128 (43.4) <0.001
Other 379 (75.8) 167 (56.6)
Experiencing physical or sexual violenceb
Yes 41 (8.2) 24 (8.2) 0.996
No 459 (91.8) 269 (91.8)
Experiencing homelessnessb
Yes 84 (16.7) 36 (12.2) 0.084
No 418 (83.3) 259 (87.8)
Recent incarcerationb
Yes 14 (2.8) 10 (3.4) 0.629
No 487 (97.2) 284 (96.6)
Engaging in sex workb,c
Yes 8 (1.6) 54 (18.3) <0.001
No 494 (98.4) 241 (81.7)
Irregular income generationb,d
Yes 491 (98.0) 292 (99.0) 0.391
No 10 (2.0) 3 (1.0)
Daily heroin useb
Yes 11 (2.2) 11 (3.7) 0.201
No 491 (97.8) 284 (96.3)
Daily stimulant useb,e
Yes 154 (30.7) 107 (36.3) 0.104
No 348 (69.3) 188 (63.7)
Binge drug useb
Yes 138 (27.5) 92 (31.2) 0.266
No 364 (72.5) 203 (68.8)
Heavy alcohol useb,f
Yes 59 (11.8) 55 (18.7) 0.007
No 442 (88.2) 239 (81.3)
Engaging in unprotected sexb
Yes 109 (21.7) 87 (29.5) 0.014
No 393 (78.3) 208 (70.5)
Enrollment in drug or alcohol treatmentb,g
Yes 282 (56.3) 177 (60.2) 0.280
No 219 (43.7) 117 (39.8)
Recent overdoseb
Yes 62 (12.4) 25 (8.5) 0.088
No 439 (87.6) 270 (91.5)
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Abbreviations: IQR: inter-quartile range; PTSD: post-traumatic stress disorder; PWUD: people who use drugs

a

symptoms endorsed in the past 30 days

b

in the past 6 months

c

Includes exchanging sex for gifts, food, shelter or clothes

d

estimates obtained using Fisher’s exact test

e

stimulants includes cocaine, crack, crystal methamphetamine, goofball or speedball

f

defined as >3 alcoholic drinks per occasion or >6 drinks per week in the past six months for women; >4 alcoholic drinks per occasion or >13 drinks in total per week in the past six months for men

g

includes use of one or a combination of opioid substitution therapy, detox programs, drug court, residential drug treatment and outpatient counseling

Gender-stratified estimates between social-structural exposures and drug use behaviours and PTSD diagnosis are reported in Table 2. In women, PTSD diagnosis remained positively and independently associated with experiencing violence (adjusted odds ratio [AOR]:3.66; 95%CI:1.14–11.72), at least daily stimulant use (AOR: 2.32; 95%CI:1.32–4.08) and heavy alcohol use (AOR:3.84; 95%CI:1.84–8.00) in the past six months, and negatively and independently associated with being in a stable relationship (AOR:0.46; 95%CI:0.25–0.84). In men, no variables were found to be independently associated with PTSD diagnosis. Gender-stratified correlates associated with PTSD symptom cluster endorsement revealed similarities in line with the main analysis (See Supplementary Table 1).

Table 2.

Bivariable and multivariable gender-stratified correlates of a probable PTSD diagnosis (≥ 31) among a cohort of PWUD in Vancouver, Canada (N= 797).

PTSD
Characteristic Women
N = 295 (37.0)		 Men
N = 502 (63.0)
OR (95% CI) AOR (95% CI) OR (95% CI) AOR (95% CI)
Age (per year older) 1.00 (0.97 – 1.02) 1.01 (0.98 – 1.03) 0.97 (0.95 – 0.99) 0.98 (0.96 – 1.01)
White ethnicity
White vs. Non-White 1.11 (0.67 – 1.83) 1.47 (0.83 – 2.63) 1.35 (0.92 – 1.97) 1.48 (0.98 – 2.21)
Relationship statusa
Legally married/common law/regular partner vs. Other 0.60 (0.38 – 0.96) 0.46 (0.25 – 0.84) 0.69 (0.44 – 1.10) 0.66 (0.39 – 1.14)
Experiencing physical or sexual violencea
Yes vs. No 4.96 (1.65 – 14.90) 3.66 (1.14 – 11.72) 2.26 (1.19 – 4.31) 1.64 (0.81 – 3.31)
Experiencing homelessnessa
Yes vs. No 1.65 (0.80 – 3.40) 1.13 (0.48 – 2.64) 2.45 (1.52 – 3.96) 1.71 (0.98 – 2.99)
Recent incarcerationa
Yes vs. No * * 2.25 (0.77 – 6.52) 1.07 (0.32 – 3.58)
Sex worka,b
Yes vs. No 1.80 (0.97 – 3.32) 1.07 (0.51 – 2.25) * *
Irregular income generationb
Yes vs. No * * 0.69 (0.19 – 2.46) 0.53 (0.14 – 2.01)
Daily heroin usea
Yes vs. No 1.06 (0.32 – 3.54) 0.48 (0.11 – 2.14) 2.67 (0.80 – 8.90) 1.67 (0.45 – 6.22)
Daily stimulant usea,c
Yes vs. No 2.66 (1.61 – 4.37) 2.32 (1.32 – 4.08) 1.38 (0.92 – 2.06) 1.02 (0.64 – 1.61)
Binge drug usea
Yes vs. No 2.05 (1.23 – 3.41) 1.70 (0.95 – 3.05) 1.61 (1.07 – 2.42) 1.31 (0.82 – 2.11)
Heavy alcohol usea,d
Yes vs. No 3.16 (1.64 – 6.10) 3.84 (1.84 – 8.00) 0.96 (0.53 – 1.73) 1.00 (0.53 – 1.89)
Engaging in unprotected sexa
Yes vs. No 1.05 (0.63 – 1.73) 1.37 (0.70 – 2.69) 1.22 (0.78 – 1.91) 1.14 (0.66 – 1.98)
Enrollment in drug or alcohol treatmenta,e
Yes vs. No 1.00 (0.63 – 1.60) 1.21 (0.71 – 2.07) 0.85 (0.58 – 1.24) 0.88 (0.59 – 1.33)
Recent overdosea
Yes vs. No 2.42 (0.98 – 5.99) 2.35 (0.87 – 6.33) 1.44 (0.83 – 2.49) 0.93 (0.49 – 1.74)
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Abbreviations: AOR: adjusted odds ratio; CI: confidence interval OR: odds ratio; PTSD: post-traumatic stress disorder; PWUD: people who use drugs

a

in the past six months

b

Includes exchanging sex for gifts, food, shelter or clothes

c

stimulants includes cocaine, crack, crystal methamphetamine, goofball or speedball

d

defined as >3 alcoholic drinks per occasion or >6 drinks per week in the past six months for women; >4 alcoholic drinks per occasion or >13 drinks in total per week in the past six months for men

e

includes use of one or a combination of opioid substitution therapy, detox programs, drug court, residential drug treatment and outpatient counselling

*

unstable estimates due to low frequencies

Both women and men with a PTSD diagnosis exhibited high proportions of PTSD symptoms across all clusters, including intrusive symptoms (96.2% vs. 100%), avoidance symptoms (87.9% vs. 91.8%), negative alterations in mood (96.8% vs. 97.5%) and cognition and negative alterations in arousal and reactivity (96.2% vs. 98.1%).

Table 3 represents brief descriptions of worst event associated with PTSD symptoms. Among women reporting a PTSD diagnosis, in reference to the event attributed to PTSD symptoms, 47.1% reported their life was in danger, 36.3% reported experiencing serious injury and 35.7% reported the event involving sexual violence. The most common worst events reported by women included sexual assault (35.1%), life-threatening illness or injury (11.5%), sudden accidental death (10.8%) and other types of stressful events (10.8%). The median length of time since the reported event was 19 years (IQR:10–30). Among men with a PTSD diagnosis, in reference to the traumatic event, 36.1% reported their life was in danger, 29.7% reported experiencing serious injury, and 20.9% reported that the event involved sexual violence. The most common worst events described by men included sexual assault (21.5%), life-threatening illness or injury (19.0%), other types of stressful events (11.4%) and physical assault (10.8%). The median length of time since the reported event was 20 years (IQR:8–40).

Table 3.

Gender-stratified descriptions of the worst traumatic event experienced by PWUD with a probable PTSD diagnosis in Vancouver, Canada (N=315).

Event Characteristic Women N=157
n (%)		 Men N=158
n (%)
How long ago the event happened
 (in years, median, IQR) 19.0 (10.0 – 30.0) 21.0 (8.0 – 40.0)
How was event experienced
 Happened to me directly 106 (67.5) 102 (64.6)
 I witnessed it 38 (24.2) 40 (25.3)
 I learned about it happening to a close family member or friend 12 (7.6) 12 (7.6)
 I was repeatedly exposed to details about it as part of my job 0 (0) 2 (1.3)
 Not reported 1 (0.6) 2 (1.3)
Was someone’s life in danger?
 Yes, my life 74 (47.1) 57 (36.1)
 Yes, someone else’s life 55 (35.0) 61 (38.6)
 No 27 (17.2) 37 (23.4)
 Not reported 1 (0.6) 3 (1.9)
Was someone seriously injured or killed?
 Yes, I was seriously injured 57 (36.3) 47 (29.7)
 Yes, someone else was seriously injured or killed 54 (34.4) 52 (32.9)
 No 45 (28.7) 56 (35.4)
 Not reported 1 (0.6) 3 (1.9)
Did it involve sexual violence?
 Yes 56 (35.7) 33 (20.9)
 No 100 (63.7) 123 (77.8)
 Not reported 1 (0.6) 2 (1.3)
Brief description of worst event
 Fire or explosion 3 (1.9) 2 (1.3)
 Transportation accident 6 (3.8) 8 (5.1)
 Serious accident at work, home or during a recreational activity 1 (0.6) 3 (1.9)
 Physical assault (with or without weapon) 12 (7.6) 17 (10.8)
 Sexual assault 52 (33.1) 34 (21.5)
 Combat or exposure to a warzone 1 (0.6) 7 (4.4)
 Captivity 10 (6.4) 2 (1.3)
 Life-threatening illness or injury 18 (11.5) 30 (19.0)
 Severe human suffering 0 (0) 1 (0.6)
 Sudden violent death 10 (6.4) 12 (7.6)
 Sudden accidental death 17 (10.8) 14 (8.9)
 Serious injury, harm or death you caused to someone 1 (0.6) 5 (3.2)
 Other stressful event or experience 17 (10.8) 18 (11.4)
 Not reported 9 (5.7) 5 (3.2)
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Abbreviations: PTSD: post-traumatic stress disorder; PWUD: people who use drugs

4.0. DISCUSSION

This study found differences in probable PTSD diagnosis between women and men in a Canadian cohort of PWUD. Specifically, women who use drugs reported a higher prevalence of PTSD compared to men. Among women, those with a PTSD diagnosis experienced a greater likelihood of exposure to violence and higher intensity substance use behaviours compared to women without the disorder. Among those with a PTSD diagnosis, both women and men demonstrated high proportions of PTSD symptoms across clusters, while women more commonly than men reported that their worst traumatic event involved sexual violence. These findings highlight important considerations for meeting the needs of PWUD with histories of trauma.

Our results indicate over half of women versus one-third of men in the sample met diagnostic criteria for PTSD. The sample’s prevalence of PTSD reflect similar yet higher proportions of the disorder across genders compared to the general population, which may be partially explained by increased rates of violence experienced by PWUD (Marshall et al., 2008; Peirce et al., 2016; Peirce et al., 2013). While men are more likely to experience traumatic events compared to women, studies indicate that women experience PTSD two-to-four times greater than men, with the lifetime prevalence of PTSD ranging from 10–12% in women and 5–6% in men in the general population (Olff, 2017). Women’s increased risk of developing PTSD may be attributed to several psychosocial and biological reasons including women’s heightened response to fear and stress, sex-based differences in the hypothalamic-pituitary-adrenal axis, and gender-based differences in coping (Inslicht et al., 2013; Najavits et al., 1997; Olff, 2017).

Gender differences in type of trauma experienced may also partially contribute to the disproportionate burden of PTSD in women. A 2006 meta-analysis by Tolin and colleagues (Tolin & Foa, 2006) across various subpopulations demonstrated that women experienced trauma related to partner violence, sexual assault, and childhood abuse, while men experienced trauma related to accidents, physical assault, natural disasters and armed conflict. A study among PWUD found that women were more likely to experience violence perpetrated by intimate partners, acquaintances and sex work clients, while men were more likely to experience violence perpetrated by strangers or police (Marshall et al., 2008). In the present sample, among those diagnosed with PTSD, few differences were found between women and men’s reports of the worst traumatic event experienced and associated with PTSD symptoms (See Table 3). However, women were more likely than men to report that their traumatic event involved sexual violence (35.7% vs, 20.9%; p<0.05). Sexual trauma and violence perpetrated by family and intimate partners carry severe and negative psychological consequences, with survivors often experiencing negative affect regulation resulting from high levels of stigma, shame and self-blame (Sullivan et al., 2016; Ullman et al., 2013). The elevated prevalence of PTSD, as well as sexual violence associated with the traumatic event among women in our sample compared to men may be explained by women who use drugs’s heightened exposure to past and recurrent gender-based trauma and violence, in addition to other research indicating higher rates of intimate partner violence, childhood abuse and sexual assault in women who use drugs compared to other subgroups of women (Kilpatrick, Acierno, Resnick, Saunders, & Best, 1997; Plotzker et al., 2007; Sullivan et al., 2016).

Our findings further revealed that women who met criteria for PTSD had a nearly four-fold increase in odds of experiencing recent physical or sexual violence compared to women without PTSD. Despite the present study’s limitations of elucidating temporality, past literature highlights women who use drugs’ complex and overlapping experiences of violence and PTSD (Bailey, Trevillion, & Gilchrist, 2019; Najavits et al., 1997; Sullivan et al., 2016; Ullman et al., 2013). Women who use drugs are more likely to report childhood sexual and physical abuse compared to men and other subgroups of women, and among women who use drugs such forms of trauma have been found to be strong predictors of adulthood trauma and revictimization (Gilbert, el-Bassel, Schilling, & Friedman, 1997; Schumm et al., 2004). Studies indicate that women who use drugs experience elevated rates of violence compared to other women (Bailey et al., 2019; Plotzker et al., 2007; Schumm et al., 2004), and subsequent adulthood re-exposure to violence among this group has been associated with adverse mental health outcomes including PTSD (Gilbert et al., 1997; Schumm et al., 2004).

Overlapping sexual and injecting networks and increased need for assisted injection among women who use drugs may further limit one’s ability to navigate risk and increase exposure to violence (Pinkham et al., 2012). In the context of a contaminated drug supply, severe intoxication and loss of consciousness attributed to fentanyl-adulterated drugs has resulted in women’s increased susceptibility to theft and/or sexual assault (J. Boyd et al., 2018). The increased odds of violence experienced by women with PTSD may be explained by the everyday forms of gender-based violence experienced by women who use drugs, which is exacerbated among those who are most structurally vulnerable (Bungay, Johnson, Varcoe, & Boyd, 2010; McNeil et al., 2014). Traumatic events and violence are stressors that are associated with a number of adverse outcomes, including distress, loss of resources, and potential development of mental health disorders such as PTSD (Peirce et al., 2016; Schumm et al., 2004). Our research highlights the potential adversities women in this setting face, including interference with the ability to cope, meet the demands of daily life, and engage with services. While our research did not reveal any independent associations among men, past research highlights the increased burden of PTSD among certain subgroups of men, including homelessness men who experience a range of traumatic exposures that increase risk of developing co-occurring disorders (Kim & Ford, 2006).

Findings additionally indicate that women who met the criteria for PTSD were more likely to report higher intensity substance use, including daily stimulant use and heavy alcohol use compared to those without PTSD. A number of studies indicate that concomitant experiences of violence and PTSD increase women’s likelihood of substance use compared to those without histories of trauma or PTSD (Khoury, Tang, Bradley, Cubells, & Ressler, 2010; Sullivan et al., 2016; Ullman et al., 2013). This may be attributed to women’s use of substances to cope with trauma and stress and reduce negative affect in comparison to men (Lehavot, Stappenbeck, Luterek, Kaysen, & Simpson, 2014). Our overlapping findings which demonstrate an increased likelihood of experiencing violence among women who use drugs with PTSD suggests that women with past or recurrent experiences of trauma may be inclined to use substances to manage the negative consequences of trauma, including the frequency and severity of PTSD symptoms (Reynolds et al., 2005; Sullivan et al., 2016). These findings are in line with existing literature on self-medication hypothesis, as well as literature that indicates that drug use preferences may be influenced by a substance’s differential effect on PTSD symptom management (Back et al., 2003). Specifically, in support of our findings, past evidence indicates that among those who experience trauma and PTSD, cocaine and other stimulants may be used for their emotionally numbing effect, whereas alcohol may be preferred for its anxiolytic and depressant properties (Najavits et al., 2003; Tull, Gratz, Aklin, & Lejuez, 2010). It is important to note that while substances may be used to manage PTSD symptoms, their effects often provide only short-term relief. Active use or withdrawal from substance’s may mirror, exacerbate or obscure frequency and severity of PTSD symptoms (Reynolds et al., 2005), thus perpetuating worsening outcomes for co-morbid conditions. Nonetheless, the varied range of substances used among those with PTSD in this sample illustrates the complex phenomenon of self-medication and highlights the important ways substance-use specific research may inform PTSD treatment and prevention efforts (Johnson et al., 2010).

Among women, being in a stable relationship was inversely associated with a probable PTSD diagnosis, indicating that stable support from a partner may buffer the relationship between trauma and PTSD or that women in stable relationships are less likely to experience trauma. This finding is line with past research conducted among US veterans that found that social support was negatively associated with PTSD (Lehavot et al., 2018). While severe manifestations of PTSD symptoms may lead to the deterioration of social networks, inadequate social support is associated with greater likelihood of PTSD development after trauma, particularly in women (Lehavot et al., 2018).

Elevated trauma and PTSD among this sample of PWUD highlight the need for specialized mental health and addiction treatment services, as well as trauma-informed, gender-sensitive health and harm reduction programming (Bailey et al., 2019; International AIDS Society, 2019). A robust evidence-base supports the need for simultaneous and integrated treatment of co-occurring disorders, as conventional mental health and substance use services may be ill-equipped to deal with patient’s complex needs (Bailey et al., 2019; Flanagan et al., 2016). Specifically, women who use drugs with histories of trauma face unique requirements, often presenting with severe clinical symptoms, experiencing difficulty being retained in care, and reporting worse SUD outcomes compared to women without trauma (Lopez-Castro et al., 2015). For women who use drugs who experience ongoing violence and severe PTSD symptoms, predominant evidence-based treatment approaches centre around integrated psycho-social educational sessions that teach coping strategies to enable emotional regulation, symptom stabilization and external safety, as well as access to safe social support networks (Bailey et al., 2019). These sessions should be made readily available through referrals or within services accessed by PWUD, including low-barrier harm reduction and treatment services (Lee et al., 2019).

Furthermore, our findings suggest that health and harm reduction services may benefit from adopting trauma-informed and gender-sensitive approaches. Trauma-informed care encompasses a service delivery approach whereby practitioners accommodate for high rates of trauma in populations they serve (Bailey et al., 2019; Killeen, Back, & Brady, 2015; Nathoo, Poole, & Schmidt, 2018). By recognizing the consequences of trauma and creating a safe environment, providers avoid retraumatizing patients and create space for healing (Bailey et al., 2019; Killeen et al., 2015). Gender-sensitive approaches are oriented toward the unique norms and inequities faced by women who use drugs (International AIDS Society, 2019; World Health Organization, 2009). In the context of the opioid crisis, SisterSpace, Canada’s first women’s-only safe consumption site, is an unique example of both trauma-informed and gender-sensitive programming (J Boyd, Lavalley, Czechaczek, Mayer, & Kerr, In Print. 2020.; Nathoo et al., 2018). Beyond preventing overdose and linking clients to other services, this service, along with other supervised consumption services have been shown to serve as safe havens against the everyday violence experienced by women who use drugs by fostering space for physical and emotional safety (Fairbairn, Small, Shannon, Wood, & Kerr, 2008; Nathoo et al., 2018). Such approaches to addressing safety and gender-based violence hold potential to address the needs of PWUD living with PTSD.

This study has several strengths. Differing from past PTSD research conducted among veteran- and clinic-based populations, this study used a community-recruited sample of PWUD, providing a gender-comparative analysis of differences associated with PTSD among people with longstanding histories of drug use. Furthermore, probable PTSD diagnosis was obtained by a validated measure administered by clinically trained research interviewers. In terms of limitations, the data were derived from non-randomized cohorts of PWUD and thus generalizability of study findings may be limited. Second, the self-reported nature of indicators, may have been subject to social desirability and recall bias due to the stigma and sensitivity associated with mental health and drug use. Third, no conclusions regarding PTSD diagnosis among transgender individuals could be drawn given the low number of participants who identified as transgender. Future research should seek to understand the relationship between substance use and PTSD among transgender individuals, as well as other gender and sexual minorities (Reisner et al., 2016). Finally, the cross-sectional nature of this study limits any conclusions related to temporality.

5.0. CONCLUSIONS

In conclusion, our findings revealed gender-based differences in relation to socio-structural factors and drug use patterns and behaviours associated with having a probable PTSD diagnosis in a cohort of PWUD. Results indicate that women meeting diagnostic criteria for PTSD were more likely to experience exposure to physical and sexual violence, as well as engage in higher intensity substance use behaviours. Accordingly, there is an urgent need to develop gender-sensitive and trauma-informed health and social programming to meet the immediate needs of PWUD with histories of trauma and PTSD.

Supplementary Material

Supplementary Tables

Acknowledgements

We would like to thank the study participants for their contributions to the research, as well as past and current researchers and staff. We would also like to thank: Dr. Ekaterina Novosa, Jennifer Matthews, Cristy Zonnefeld, Steve Kain and Ana Prado for their research and administrative assistance.

Role of funding source

This study was supported by the United States National Institutes of Health (US-NIH; Grants U01-DA038886 and U01-DA021525) and the Canadian Institutes of Health Research (CIHR; MOP-286532; 20R74326). Sanjana Mitra is supported by a CIHR Frederick Banting and Charles Best Graduate Scholarship Doctoral Award (CGS-D). M-J Milloy is supported in part by the US NIH (U01-DA021525), a New Investigator Award from the CIHR and a Scholar Award from the Michael Smith Foundation For Health Research (MSFHR). Kanna Hay- ashi is supported by a CIHR New Investigator Award (MSH-141971), a MSFHR Scholar Award and the St. Paul’s Foundation. Thomas Kerr is supported by a CIHR Foundation grant (20R74326). This research was undertaken, in part, thanks to funding from the Canada Research Chairs program through a Tier 1 Canada Research Chair in Inner City Medicine, which supports Evan Wood.

Declaration of Competing Interest

Dr. M-J Milloy’s institution (the University of British Columbia) has received an unstructured gift from NG Biomed Ltd., a private firm seeking a government license to produce medical cannabis, to support him. He is the Canopy Growth professor of cannabis science, a position established through unstructured gifts to the University of British Columbia from Canopy Growth, a licensed producer of cannabis, and the Government of British Columbia’s Ministry of Mental Health and Ad- dictions. Evan Wood is supported by the Canada Research Chairs pro- gram through a Tier 1 Canada Research Chair in Addiction Medicine. Dr. Wood is also a consultant to a mental health wellness company called Numinus. All other authors report no competing interests in relation to the work.

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Supplementary Materials

Supplementary Tables
NIHMS1677675-supplement-Supplementary_Tables.pdf (174.4KB, pdf)

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