Introduction

Violence among people who use illegal drugs (PWUD) is common and is associated with elevated risks for significant health and social harm. Many past studies, from a range of international settings, have shown that drug use can increase the risk of both violent perpetration and victimization [1, 2]. The pervasiveness of violence among PWUD has been explained in part by Goldstein’s framework [3] that describes the role of psychopharmacological, economic, and structural factors in perpetuating violence among PWUD. This model suggests that violence may be influenced by drug-induced states such as hyperactivity or reduced vigilance (i.e., pharmacological factors), committing violent crime such as robbery to obtain drugs or money for drugs (i.e., economic factors), and the inherent dangers associated with the illegal drug trade (i.e., systemic factors) [3]. Solutions to reduce and prevent violence among PWUD have come mostly in the form of increased law enforcement [4]. However, recent evidence suggests that enforcement-based interventions have potential to exacerbate violence in the population [5, 6]. Given the harmful outcomes associated with violence at both the individual and community-level, there is a need to identify and intervene upon other factors that serve to perpetuate violent victimization, including those that go beyond the pharmacological and structural factors outlined above.

One factor that may play a role in perpetuating violence is childhood trauma, although this has not received much attention in the literature on violence among PWUD. Given that exposure to childhood maltreatment increases the risk of developing a substance use disorder (SUD) later in life [7], it is not surprising that childhood trauma is common among adult PWUD [8, 9]. Indeed, the connection between childhood trauma and SUD has been well-documented [10–12], and has been explained using the self-medication theory [13], which suggests that individuals may develop a SUD by treating or muting negative psychological symptomology with drugs or alcohol [13]. For example, the numbing or euphoric effects of opioids can be effective in temporarily relieving the psychological distress experienced from posttraumatic stress disorder (PTSD) [14]. This theory has been supported by studies that show the effect of trauma cues on drug cravings [15, 16] and the effectiveness of trauma-focused therapy in decreasing substance use [16, 17].

While there has been a growing number of studies done in the last two decades examining the role that childhood trauma plays in adult victimization [18–21], little attention has been given to the specific role that childhood physical abuse may play in perpetuating violent victimization among adult PWUD. There is also a need to examine the phenomenon of revictimization as it relates to non-sexual physical assault to help fill the gap in revictimization literature (which has historically focused on sexual revictimization) by studying the experiences of individuals who report histories of non-sexual childhood physical abuse, as revictimization typically occurs within the same category of violence [22]. Accordingly, this study sought to investigate whether childhood trauma as a result of physical abuse is associated with recent violent victimization among a cohort of PWUD in Vancouver, Canada.

Methods

Results

Data from 2960 PWUD were included in this study. Among this sample, 1018 (34.39%) were female, 1393 (47.06%) were BIPOC, and the median age was 32.1 years (Interquartile Ratio [IQR]: 23.26–43.46). The number of participants who reported a history of moderate to extreme childhood physical abuse was 1030 (34.8%) and 949 (32.06%) participants reported recent violent victimization (being physically assaulted in the last six months) at baseline. Of the 949 participants who reported physical assault, 399 (42.04%) were also victims of childhood physical abuse. In 16,597 interviews between 2005 and 2018, recent violent victimization was reported in 3329 (20.1%) interviews. Characteristics of the study sample stratified by violent victimization at baseline are presented in Table 1.

In bivariate analysis, childhood physical abuse was positively associated with subsequent violent victimization (Odds Ratio [OR] = 1.33, 95% confidence interval [CI]: 1.21–1.46, p < 0.001). Other factors associated with recent violent victimization in bivariate analyses included: belonging to the ARYS cohort (OR = 2.28, 95% CI: 2.03–2.57), belonging to the VIDUS cohort (OR = 1.27, 95% CI: 1.13–1.43), younger age (OR = 0.97, 95% CI: 0.96–0.97), male sex (OR = 1.25, 95% CI: 1.13–1.38), being heterosexual (OR = 1.20, 95% CI: 1.06–1.36), white ethnicity (OR = 1.32, 95% CI: 1.21–1.45), homelessness in the last six months (OR = 1.90, 95% CI: 1.76–2.04), sex work in the last six months (OR = 1.29, 95% CI: 1.15–1.44), drug dealing in the last six months (OR = 1.74, 95% CI: 1.61–1.87), receiving any kind of drug or alcohol treatment in the last six months (OR = 0.92, 95% CI: 0.85–0.99), and current heavy alcohol use (OR = 1.24, 95% CI: 1.14–1.35).

As shown in Table 2, in our multivariate analysis, two variables (being heterosexual and receiving any kind of drug or alcohol treatment in the last six months) did not retain significance. Childhood physical abuse remained independently associated with subsequent violent victimization, after adjustment for other potential confounders (Adjusted Odds Ratio [AOR] = 1.34, 95% CI: 1.23–1.46, p < 0.001).

Discussion

In the present study, we found that childhood physical abuse was common among PWUD, with approximately one third (34.8%) of the sample reporting moderate to extreme childhood physical abuse. Likewise, almost one third (32.06%) of PWUD reported violent victimization in the last six months at baseline. In a multivariate longitudinal analysis, we found that childhood physical abuse remained positively associated with recent violent victimization after adjustment for a range of potential confounders, with those who experienced moderate to extreme childhood physical abuse having approximately one and a half times higher odds of violent victimization.

To our knowledge, this is the first study to examine the relationship between recent violent victimization and childhood physical abuse among PWUD. While most research on violence and substance use attributes violence to the psychoactive effects of drugs, structural factors, or the consequences associated with the prohibition of illegal drugs [26–28], our findings highlight the possible developmental and psychological antecedents of violent victimization among this population.

One proposed explanation for why revictimization occurs in these cases is the psychological effect that childhood abuse in general has on early life, as described by object relations theory [29]. This model suggests that during childhood, repeated abuse perpetrated by a caregiver forms a collection of deleterious perceptions and expectations of relationships, which are subsequently activated in adulthood [30]. Due to its typically repetitive and prolonged nature [31], childhood abuse in all forms can promote the development of complex PTSD [32], which in turn, has been widely linked to a heightened risk of revictimization [33]. Related symptoms include self-doubt, difficulty perceiving and responding to threats, expectation of pain and injury in relational contexts, and dissociation [29, 34, 35]. These psychological adaptations to the difficult circumstances of childhood physical abuse can unfortunately lead to self-destructive behaviour in adulthood that further increases the risk of violent victimization.

An alternative and equally compelling explanation for why childhood physical abuse may lead to future revictimization is the neurological damage precipitated by trauma [36]. Due to the neuroplasticity of the brain in early life [37], studies have found all forms of childhood abuse to be linked to the underdevelopment of the left hemisphere and hippocampus, which negatively affects logical thinking and memory [38]. Additionally, childhood abuse is linked to: diminished right-left hemisphere integration, which results in slower processing of information and cognitive avoidance [38, 39]; abnormalities in the cerebellar vermis, which plays an important role in regulating attention and emotion [38]; and dysfunction of the temporolimbic system [38], which impairs one’s judgement of others’ emotional states [40]. These negative brain adaptations could promote the risk of being victimized via a decreased ability for decision-making related to self-protection.

This study has limitations. First, the cohorts included in this study are community-recruited and not random samples, therefore the findings may not represent trends in the general population of people who use drugs. Second, our data was collected via self-reports and therefore response biases may have affected participant responses. Specifically, in regard to childhood trauma, reports may be influenced by a recall bias wherein individuals who repeatedly suffer difficult events throughout their lives are more likely to remember their adverse childhood experiences [41]. While some may be unable to recall memories of early victimization, others (for example, those reporting recent physical assault) may have stronger memories of childhood abuse, due to the perceived relevance of these events and a tendency to re-tell these stories in a search for meaning [41]. Finally, this study was observational in nature and therefore causality cannot be inferred from its findings.

Collectively, these findings support the need for a preventative, victim-centered, and trauma-informed approach to reducing the high rate of violent victimization among PWUD. Screening this population for childhood trauma in healthcare and other relevant facilities is recommended. Interventions such as trauma-focused cognitive behavioural therapy (TF-CBT) should be provided, as it has been proven to be an effective treatment for reducing the complex PTSD symptoms suffered by victims of childhood abuse [42]. It is important that such counselling services be made easily accessible for PWUD, given its potential to lower the rate of violence among PWUD by treating its associated psychological factors.

In conclusion, this study found that about one-third of surveyed PWUD in Vancouver, Canada have a history of childhood physical abuse, and that this form of trauma was independently and positively associated with subsequent violent victimization in adulthood. Future research should seek to elucidate the specific psychological mechanisms through which childhood trauma increases the likelihood of victimization in adulthood. Additionally, PWUD should be given greater access to evidence-based interventions (such as TF-CBT) that are aimed at improving safety for individuals with histories of childhood abuse.

Acknowledgments

The authors thank the study participants for their contribution to the research, as well as current and past researchers and staff at the British Columbia Centre on Substance Use.