Interpersonal violence is a global public health concern and a leading cause of injury, disability, and mortality worldwide. Although most individuals with psychiatric diagnoses do not engage in violent acts, existing evidence suggests that interpersonal violence is highly prevalent among individuals with psychiatric disorders. For example, individuals with serious mental illness incur approximately 2 to 3 times greater risk for interpersonal violence, while individuals with both serious mental illness and substance use disorders incur risk up to 10 times that of healthy individuals.1-3
Interpersonal violence in individuals with psychiatric conditions is not only a significant clinical concern for health care providers, caregivers, and loved ones, but also a substantial stigmatizing factor for mental health populations. While most individuals with psychiatric conditions will not use violence in their lifetime, the empirical link between interpersonal violence and mental illness perpetuates impairment associated with the condition and presents a barrier to treatment-seeking.
There is tremendous heterogeneity in the frequency, severity, and type of violent episodes, with whom the violence occurs (ie, general aggression versus intimate partner violence or other family violence), as well as the etiology and course in both psychiatric and general populations. Thus, there is agreement in the literature that while developing screening and intervention approaches with a high degree of reach is useful, a one-size-fits all approach to screening and intervention of interpersonal violence is inadequate.
Two psychiatric conditions, in particular, have been identified as salient correlates of interpersonal violence perpetration and victimization. The following is a brief review of the literature PTSD and substance use disorders (SUD), as well as their co-occurrence with interpersonal violence. In addition, screening tools and existing data regarding intervention strategies to prevent and reduce interpersonal violence in the context of PTSD and SUD are also briefly review.
Co-occurrence of PTSD and SUD
PTSD and SUD, which commonly co-occur with one another, are among the most frequently identified psychiatric correlates of interpersonal violence. In the US, up to 40% of individuals with SUD also meet diagnostic criteria for PTSD.4 Individuals with co-occurring PTSD and SUD incur heightened risk for other psychiatric problems (eg, depression, anxiety), suicidality, neuropsychological impairment, increased morbidity and mortality, unemployment, and social impairment. Co-occurring PTSD and SUD also places a tremendous economic burden on the health care system, as individuals with this complex dual condition have poorer treatment outcomes on multiple indices of functioning, longer duration of substance use, and more treatment episodes.
Related content: 7 Measures for Screening and Assessing IPV
Associations between interpersonal violence, PTSD, and SUD
PTSD has been commonly and causally linked to use of interpersonal violence among a variety of populations, including men and women in civilian and military populations, students, and treatment-seeking samples.3,5-7 The association between PTSD and interpersonal violence has often been explained by social information processing theories positing that PTSD can predispose individuals to hostile attribution bias, increased perception of threat, and heightened stress reactivity, thereby precipitating a propensity toward maladaptive stress responding, including interpersonal violence.
Substance misuse and SUD are also salient risk factors for both interpersonal violence victimization and use of interpersonal violence. Alcohol use has shown the most unequivocal causal effects. For example, rates of interpersonal violence perpetration are up to 8-fold higher among individuals with, as compared to without, alcohol use disorder.8 Moreover, interpersonal violence episodes are more frequent and severe in the presence of alcohol use.9Findings suggests a dose-response effect between alcohol use and interpersonal violence severity.10
The association between alcohol use and interpersonal violence is most commonly explained by the alcohol myopia theory, which suggests that the pharmacological effects of alcohol simultaneously cause a reduction in the scope of one’s attentional focus to the most salient cues in the environment and reduce the capacity to engage adaptive cognitive abilities. Thus, under the context of acute intoxication, provocative cues such as interpersonal conflict instigate aggressive behavior.
The effects of drug use on interpersonal violence is less clear. Although drug use and drug-related problems are correlated with interpersonal violence, very little research has been done to examine casual links. Stimulants, such as cocaine and amphetamines, are the drugs most frequently linked to interpersonal violence. There is some evidence to suggest that high doses of cocaine are associated with aggressive responding and cocaine use has an impact on same-day interpersonal violence.11
Research examining associations between cannabis and interpersonal violence is mixed. Cannabis may increase the risk for interpersonal violence, while other data suggest it decreases subjective feelings of aggression and aggressive responding.12 The link between other drugs, such as opioids and benzodiazepines, and interpersonal violence is not as strong. Opioid use has been positively associated with interpersonal violence while other research suggests that opioid use may have stronger associations with interpersonal violence victimization.13 There is a great deal more work to be done on the distinct and combined associations between different drugs and interpersonal violence, as well as the pharmacologic and behavioral mechanisms explaining their effects on aggressive behavior.
Several studies have examined the combined and relative associations of PTSD and substance use on interpersonal violence. While additional research is urgently needed in this area, findings consistently suggest that these disorders independently and collectively increase risk for interpersonal violence.
In an extension of the alcohol myopia model, the more complex I-cubed (instigation, impellance, inhibition) model posits that interpersonal violence might be potentiated by a combination instigating stimuli paired with cognitive and contextual factors that compel and/or disinhibit one toward violence.14 Despite abundant evidence that PTSD and SUD commonly co-occur, and that these two diagnoses are among the most well-documented and salient risk factors for interpersonal violence, no studies have directly integrated PTSD diagnoses or symptom severity into an empirical examination of the alcohol myopia or I-cubed model. Closing this gap in the theoretical and empirical literature is a critical next step for the interpersonal violence field so that prevention and intervention efforts can be improved.
Dr Flanagan is Associate Professor, Medical University of South Carolina, Charleston, SC; and Staff Psychologist, Ralph H Johnson VAMC. Dr Jarnecke is Assistant Professor, Medical University of South Carolina, Charleston, SC.
The authors report no conflicts of interest concerning the subject matter of this article.
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