Does cannabis use predict aggressive or violent behavior in psychiatric populations? A systematic review

"Weeding out" violence? Translational perspectives on the neuropsychobiological links between cannabis and aggression

Recent shifts in societal attitudes towards cannabis have led to a dramatic increase in consumption rates in many Western countries, particularly among young people. This trend has shed light on a significant link between cannabis use disorder (CUD) and pathological reactive aggression, a condition involving disproportionate aggressive and violent reactions to minor provocations. The discourse on the connection between cannabis use and aggression is frequently enmeshed in political and legal discussions, leading to a polarized understanding of the causative relationship between cannabis use and aggression. However, integrative analyses from both human and animal research indicate a complex, bidirectional interplay between cannabis misuse and pathological aggression. On the one hand, emerging research reveals a shared genetic and environmental predisposition for both cannabis use and aggression, suggesting a common underlying biological mechanism. On the other hand, there is evidence that cannabis consumption can lead to violent behaviors while also being used as a self-medication strategy to mitigate the negative emotions associated with pathological reactive aggression. This suggests that the coexistence of pathological aggression and CUD may result from overlapping vulnerabilities, potentially creating a self-perpetuating cycle where each condition exacerbates the other, escalating into externalizing and violent behaviors. This article aims to synthesize existing research on the intricate connections between these issues and propose a theoretical model to explain the neurobiological mechanisms underpinning this complex relationship.

The company you keep: The neglected role of affiliating with delinquent friends in the development of the cannabis-violence link

A growing body of research suggests a potential role of cannabis use on aggressive behaviors. In literature on adolescents, the lack of consideration of important confounders, such as adolescent's affiliation with delinquent peers, limits the possibility to determine whether there might be a direct or indirect link between cannabis use and aggression. Therefore, we sought to examine the effect of delinquent peers on the association between cannabis use and violence. We re-analyzed data from 850 ninth graders who were followed from mid-adolescence to early adulthood. Generalized Estimations Equations (GEE) were conducted to examine whether affiliation with delinquent peers may mediate the relationship between cannabis use and violence. Cross-Lagged Panel Models were also conducted to estimate the directionality of these relationships over time. We additionally tested whether similar relationships may be identifiable when examining rule-breaking behaviors and/or alcohol use. GEE models revealed that both cannabis use and affiliation with delinquent peers were statistically associated with aggressive behaviors. Cannabis use, alcohol use and delinquent peers also predicted rule-breaking behaviors. More precisely, cross-lagged models showed that affiliation with delinquent peers played a partially mediating role in the cannabis-aggression link, and that similar cross-lagged estimates were observed when examining rule-breaking behaviors instead of aggression. Our results indicate that cannabis use may be associated with aggression as well as rule-breaking behaviors, suggesting a broader effect on conduct problems. More importantly, our study highlights the non-negligible role of affiliating with delinquent peers during adolescence.

Endocannabinoid system and aggression across animal species

This narrative review article summarizes the current state of knowledge regarding the relationship between the endocannabinoid system (ECS) and aggression across multiple vertebrate species. Experimental evidence indicates that acute administration of phytocannabinoids, synthetic cannabinoids, and the pharmacological enhancement of endocannabinoid signaling decreases aggressive behavior in several animal models. However, research on the chronic effects of cannabinoids on animal aggression has yielded inconsistent findings, indicating a need for further investigation. Cannabinoid receptors, particularly cannabinoid receptor type 1, appear to be an important part of the endogenous mechanism involved in the dampening of aggressive behavior. Overall, this review underscores the importance of the ECS in regulating aggressive behavior and provides a foundation for future research in this area.

Avatar Intervention for Cannabis Use Disorder in Individuals with Severe Mental Disorders: A Pilot Study

Cannabis use disorder (CUD) is a complex issue, even more so when it is comorbid with a severe mental disorder (SMD). Available interventions are at best slightly effective, and their effects are not maintained over time. Therefore, the integration of virtual reality (VR) may increase efficacy; however, it has not yet been investigated in the treatment of CUD. A novel approach, avatar intervention for CUD, uses existing therapeutic techniques from other recommended therapies (e.g., cognitive behavioral methods, motivational interviewing) and allows participants to practice them in real-time. During immersive sessions, participants are invited to interact with an avatar representing a significant person related to their drug use. This pilot clinical trial aimed to evaluate the short-term efficacity of avatar intervention for CUD on 19 participants with a dual diagnosis of SMD and CUD. Results showed a significant moderate reduction in the quantity of cannabis use (Cohen's d = 0.611, p = 0.004), which was confirmed via urinary quantification of cannabis use. Overall, this unique intervention shows promising results. Longer-term results, as well as comparison with classical interventions in a larger sample, are warranted through a future single-blind randomized controlled trial.