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.

BackgroundIneffective cannabis regulatory frameworks such as prohibition have sparked interest in alternative solutions to reduce individual and societal harms. While it has been suggested that the recreational legalization process has yielded early successes, the relatively recent implementation of the novel policies has provided a modest time frame for a truly thorough establishment and assessment of key population-level indicators. The following systematic review focuses on identifying the downstream public health sequelae of cannabis legalization policies, including parameters such as cannabis consumption rates, hospitalization rates, vehicular accidents and fatalities, criminal activity, and suicidal behaviors, as well as other substance use trends.MethodsAn exhaustive search of the MEDLINE and Google Scholar databases were performed to identify high-quality (1) longitudinal studies, which (2) compared key public health outcomes between regions which had and had not implemented recreational cannabis legalization (RML) policies, (3) using distinct databases and/or time frames. Thirty-two original research articles were retained for review.ResultsAdult past-month cannabis consumption (26+ years) seems to have significantly increased following RML, whereas young adult (18–26 years) and adolescent (12–17 years) populations do not show a significant rise in past-month cannabis use. RML shows preliminary trends in increasing service use (such as hospitalizations, emergency department visits, or poisonings) or vehicular traffic fatalities. Preliminary evidence suggests that RML is related to potential increases in serious/violent crimes, and heterogeneous effects on suicidal behaviors. While the research does not illustrate that RML is linked to changing consumptions patterns of cigarette, stimulant, or opioid use, alcohol use may be on the rise, and opioid prescribing patterns are shown to be significantly correlated with RML.ConclusionThe current data supports the notion that RML is correlated with altered cannabis consumption in adults, potentially increased criminal activity, and a decline in opioid quantities and prescriptions provided to patients. Future work should address additional knowledge gaps for vulnerable populations, such as individuals with mental health problems or persons consuming cannabis frequently/at higher THC doses. The effects of varying legalization models should also be evaluated for their potentially differing impacts on population-level outcomes.

Background and Aims Social norms and legality surrounding the use of medical and recreational cannabis are changing rapidly. The prevalence of cannabis use in adolescence is increasing. The aim of this study was to assess any sex‐based neurobiological effects of chronically inhaled, vaporised cannabis on adolescent female and male mice. Methods Female and male mice were exposed daily to vaporised cannabis (10.3% Δ‐9‐tetrahydrocannabinol [THC] and 0.05% cannabidiol [CBD]) or placebo from postnatal day 23 to day 51. Following cessation of treatment, mice were examined for changes in brain structure and function using noninvasive multimodal magnetic resonance imaging (MRI). Data from voxel‐based morphometry, diffusion weighted imaging and rest state functional connectivity were registered to and analysed with a 3D mouse atlas with 139 brain areas. Following imaging, mice were tested for their preference for a novel object. Results The effects were sexually dimorphic with females showing a unique distribution and inverse correlation between measures of fractional anisotropy and apparent diffusion coefficient localised to the forebrain and hindbrain. In contrast males displayed significant increased functional coupling with the thalamus, hypothalamus and brainstem reticular activating system as compared with controls. Cannabis males also presented with altered hippocampal coupling and deficits in cognitive function. Conclusion Chronic exposure to inhaled vaporised cannabis had significant effects on brain structure and function in early adulthood corroborating much of the literature. Females presented with changes in grey matter microarchitecture, while males showed altered functional connectivity in hippocampal circuitry and deficits in object recognition.

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