Violence and Cannabis Use: A Focused Review of a Forgotten Aspect in the Era of Liberalizing Cannabis

Abstract

There has been a shift surrounding societal and legal perspectives on cannabis reflecting changing public attitudes towards the perceived safety and social acceptability of cannabis use. With cannabis liberalization internationally, the focus of most cannabisrelated harms has been on effects with users themselves. Harm-to-others including injuries from violence have nevertheless been unfortunately largely overlooked. While studies remain heterogeneous, there is meta-analytical evidence pointing towards an association. The aims of this focused review are twofold: (I) review the evidence from meta-analyses on the association between cannabis and violence; and (II) provide an overview of possible mechanisms relating cannabis use to violence. First, evidence from meta-analytical studies in youths, intimate partners, and individuals with severe mental disorders have shown that there is a global moderate association between cannabis use and violence, which is stronger in the latter more at-risk population. Preliminary data has even highlighted a potential dose-response relationship with larger effects in more frequent users. Although of importance, this subject has remained essentially forgotten as a public health concern. While literature remains inconclusive, data has suggested potential increases in cannabis use following liberalization policies. This may increase violent outcomes if the effect is directly related to the use of cannabis by means of its psychophysiological modifications. However, for the moment, the mechanisms associating cannabis use and violence remain to be clearly resolved. Considering the recency of policy changes on cannabis, further methodologically sound research using longitudinal designs should examine the effects that cannabis use may have on different forms of violence and the trends that emerge, while evaluating the effects of possible confounding factors (e.g. other substance use). In addition, as evidence-based research from meta-analyses have shown that cannabis use is associated with violence, measures must be taken to mitigate the risks.

Evaluation of State Cannabis Laws and Rates of Self-harm and Assault

“…Although no states explicitly regulated potency, we hypothesized that THC dose may affect the association between cannabis commercialization and violent injury. 15 , 35 , 37 Thus, we tested a 6-category version of the exposure variable that separated states with recreational dispensaries into those with and without THC dose-related restrictions (defined as limiting any of the following: THC dose per serving size, THC content per package, or product types, eg, bans on edible products). 46 , 47 We also tested a 3-category exposure variable (no law vs any medical law vs any recreational law) and conducted analyses restricted to state-months with some form of cannabis legalization law (medical laws without dispensaries was the reference category).…”

“… 37 Provisions affecting consumer THC doses may be especially relevant for violence-related outcomes. 15 These policy differences matter: medical and recreational cannabis legalization per se are not consistently associated with population-level cannabis outcomes, but rates of cannabis use and poison control center calls for cannabis exposures have increased when states permit retail sales through dispensaries. 35 , 38 …”

The legalisation of cannabis: A security-vetting dilemma

“…28 Moreover, evidence from worldwide population data indicates that approximately 6,5 per cent of cannabis users have a CUD. 29 The effect of cannabis is also determined by the potency of the content of delta-9-tetrahydrocannabinol (Δ9-THC), the psychoactive key ingredient, in relation to cannabidiol (the Δ9-THC to CBD ratio).…”

The Link Between Cannabis Use and Violent Behavior in the Early Phase of Psychosis: The Potential Role of Impulsivity

“…Despite recent evidence on the link between CU and VB in psychosis, the relationship needs to be further explored, as there are still contradictory results, some studies not finding a link between CU and VB ( 38 , 63 ). These contradictory results may be due to theoretical limitations, such as differing definitions and assessments of violence; or methodological limitations, such as: the predominance of cross-sectional or retrospective studies, the failure to account for confounding factors (i.e., previous delinquent behavior, co-morbid personality disorders, dose of used substance, etc.…”

“…It should also be noted the scarcity of data on offender samples, or lack of objective and detailed data on the CU characteristics such as type, dose, and frequency of use ( 38 ). Moreover, there are insufficient empirically data of what underlies this relationship ( 38 , 39 , 63 ).…”