Association Between the Use of Cannabis and Physical Violence in Youths: A Meta-Analytical Investigation

"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.

High times and troubled relationships: Recreational marijuana laws and intimate partner violence

This study explores the relationship between Recreational Marijuana Laws (RMLs) and intimate partner violence (IPV). While marijuana is often considered harmless, the existing medical literature reveals both positive and negative impacts of its active ingredient on brain function. Utilizing a difference-in-difference methodology spanning 2006-2016 across 39 states, we find that RMLs produce a 20 percent increase in IPV incidents per 100,000 individuals, which appears to be mediated through mental health issues and binge drinking. These findings highlight the likely need for preventive and proactive policies to address the complex interplay of marijuana, RMLs, and IPV.

Associations of cannabis use, use frequency, and cannabis use disorder with violent behavior among young adults in the United States

BACKGROUND

Most violent crimes (52 %) are committed by adults aged 18-34, who account for 23 % of the US population and have the highest prevalence of cannabis use and cannabis use disorder (CUD). We examined whether and how associations of cannabis use, use frequency, and CUD with violent behavior (i.e., attacking someone with the intent to harm seriously) vary by sex in U.S. young adults.

METHODS

Data were from 113,454 participants aged 18-34 in the 2015-2019 US National Surveys on Drug Use and Health, providing nationally representative data on cannabis use, CUD (using DSM-IV criteria), and violent behavior. Descriptive analyses and bivariate and multivariable logistic regression analyses were conducted.

RESULTS

Among U.S. adults aged 18-34, 28.9 % (95 % CI = 28.5-29.2 %) reported past-year cannabis use (with/without CUD), including 20.5 % (95 % CI = 20.2-20.8 %) with non-daily cannabis without CUD, 4.7 % (95 % CI = 4.5-4.8 %) with daily cannabis use without CUD, 2.1 % (95 % CI = 1.9-2.2 %) with non-daily cannabis use and CUD, and 1.7 % (95 % CI = 1.5-1.8 %) with daily cannabis use and CUD. Past-year adjusted prevalence of violent behavior was higher among males with daily cannabis use but without CUD (2.9 %, 95 % CI = 2.4-2.7 %; adjusted prevalence ratio (PR) = 1.7, 95 % CI = 1.3-2.2) and males with daily cannabis use and CUD (3.1 %, 95 % CI = 2.3-4.0 %; adjusted PR = 1.8, 95 % CI = 1.3-2.4) than males without past-year cannabis use (1.7 %, 95 % CI = 1.6-1.9 %). Adjusted prevalence of violent behavior was higher among females with cannabis use regardless of daily cannabis use/CUD status (adjusted prevalence = 1.6-2.4 %, 95 % CIs = 0.9-3.2 %; adjusted PRs = 1.6-2.4, 95 % CI = 1.3-3.2) than females without past-year cannabis use (1.0 %, 95 % CI = 0.9-1.1 %).

CONCLUSIONS

Research is needed to ascertain the directionality of the associations between cannabis use and violent behavior and underlying sex-specific mechanism(s). Our results point to complex sex-specific relationships between cannabis use frequency, CUD, and violent behavior and highlight the importance of early screening for and treatment of CUD and of preventive interventions addressing cannabis misuse.

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.

Mental Telehealth Utilization Patterns Among High School Students from Racial and Ethnic Minority Backgrounds Affected by Violence and Substance Use

BACKGROUND

Recent data show high school students from racial and ethnic minority (REM) backgrounds in the United States confront a twofold challenge, marked by the highest rates of firearm-related homicides since 1994 and increased youth substance use. The pandemic increased online and telehealth usage opportunities for at-risk REM youth. Therefore, this study investigated (1) the frequency and prevalence of co-occurring youth violence and substance use among REM adolescents, (2) racial/ethnic, age, and natal sex (as gender data was not collected) differences in patterns and trends in co-occurring youth violence and substance use among REM adolescents, and (3) the relationship between these syndemic issues and REM adolescent mental telehealth use during the pandemic.

METHODS

Data was sourced from a nationally representative sample of U.S. 9th-12th students (n = 3241) who completed the CDC's 2021 Adolescent and Behavioral Experiences Survey (ABES). Using univariate (frequency distribution), bivariate (Pearson's chi-squared test), and multivariate logistic regression models, we examined seven violence victimization outcomes, four violence perpetration outcomes, two family violence outcomes, and six substance use outcomes and their associations with telehealth use for mental health (dependent variable) among REM adolescents.

RESULTS

This sample was primarily female (50.7%), Black or African American (48.3%), Hispanic or Latinx (20.6%), and identified as straight or heterosexual (69.5%). The study found significant sex-based differences in violence perpetration/victimization, substance use, and telehealth use for mental health. In general, mental telehealth use was significantly associated with substance use among REM adolescents (cigarette smoking, vaping, alcohol, marijuana, prescription meds, and illicit drug use) (p-value = .001). Mental telehealth use was also significantly associated with all peer and family violence outcomes (p < 0.001). Controlling for covariates, gun carrying was associated with 4.8 times higher odds of using mental telehealth. Students in a physical fight or carrying a weapon (gun, knife, or club) on school property had 2.45 times and 8.09 times the odds of utilizing mental telehealth. Bullied students were 2.5 times more likely to use mental telehealth (p-value < 0.05). Illicit drug use (cocaine, heroin, methamphetamines, and ecstasy) was associated with a higher likelihood of mental telehealth use (AOR = 1.3, p-value = .05).

CONCLUSION

Our results suggest crucial insights for shaping violence and substance use prevention strategies, with implications for the future of online and telehealth behavioral services. Mental telehealth help-seeking emerges as a crucial avenue for supporting adolescents affected by violence and substance use, especially when they face obstacles to accessing traditional services. It can work in tandem with in-person services to address these challenges.

Attitudes of Individuals with Alcohol and Substance Addiction Towards Violence Against Women

The aim of this study was to determine the attitudes of alcohol and substance dependent individuals towards violence against women. This cross-sectional study was completed with n=105 patients who were followed up in the Alcohol and Substance Addiction Treatment and Research Center of a state hospital. In this study, personal information form and ISKEBE attitudes towards violence against women scale were used as data collection tools. Among the patients diagnosed with alcohol-substance use disorder, n=53 (60.9%) were between the ages of 18-34 and n=70 (66.7%) were single. Of the patients, n=36 (52.2%) had been exposed to any type of domestic violence. The attitude scores of patients diagnosed with alcohol-substance use disorder towards violence against women were measured as 99.89 ± 22.1. In the current study, patients diagnosed with alcohol-substance use disorder who were male, lived in rural areas, had poor income status and had low educational level were found to have negatively low attitudes towards violence against women. In conclusion of this study, further studies and practices to determine and improve attitudes towards violence against women in patients diagnosed with alcohol-substance use disorder are recommended.

Adolescent Cannabis Use, Comorbid Attention-Deficit/Hyperactivity Disorder, and Other Internalizing and Externalizing Disorders

Cannabis use often co-occurs with attention-deficit/hyperactivity disorder and other internalizing and externalizing disorders. Treatment planning, including pharmacologic and psychosocial interventions, for these comorbid disorders require thorough diagnostic evaluation to determine the extent of social, emotional, and behavioral impairments, severity of substance use, and motivation for change. Improved understanding of these comorbid disorders will inform treatment planning that address current symptoms and behaviors and may also prevent the development of mental health and substance use disorders in early adulthood.

Modeling state- and trait-level associations between aggression, somatic symptoms, substance use, and distress tolerance

The current study examined the state- and trait-level associations of psychological and physical aggression to somatic symptoms, and alcohol and drug use and tested the influence of distress tolerance on these associations, while controlling for stress, sex, and minority status. A naturalistic observation was used to collect data with a sample of 245 college students at three time points with 2 weeks apart. Random-intercept cross-lagged panel models were used to disaggregate within-person effects (autoregressive and cross-lagged effects) from the between-person (latent trait-level) associations. The findings revealed that there were autoregressive effects of psychological aggression between Time 1 (T1) and Time 2 (T2) and of physical aggression between T1 and T2. There was a bidirectional association between psychological aggression and somatic symptoms at T2 and Time 3 (T3), in which T2 psychological aggression predicted T3 somatic symptoms and verse vera. T1 drug use predicted T2 physical aggression, which in turn predicted T3 somatic symptoms, indicating physical aggression being a mediator between earlier drug use and later somatic symptoms. Distress tolerance was negatively associated with psychological aggression and somatic symptoms, respectively, and such an influence did not differ across time occasions. The findings indicated the importance of incorporating physical health in the prevention and intervention of psychological aggression. Clinicians may also consider including psychological aggression in the screening of somatic symptoms or physical health. Empirical-supported therapy components for enhancing distress tolerance may help mitigate psychological aggression and somatic symptoms.

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.

Impact of cannabis on outcome in patients following traumatic injury

INTRODUCTION

Outcomes of trauma patients who tested positive for cannabis at the time of admission showed variable results. Sample size and research methodology that was used in prior studies may have resulted in the conflict. The purpose of the study was to evaluate the impact of cannabis use on outcomes in trauma patients using national data. Our hypothesis was that the use of cannabis will impact outcomes.

METHODS

The trauma quality improvement program (TQIP) Participant Use File (PUF) database of the calendar years 2017 and 2018 were accessed for the study. All trauma patients aged 12 years old and above who were tested for cannabis at the time of initial evaluation were included in the study. Variables included in the study were: race, sex, injury severity score (ISS), Glasgow Coma Scale (GCS) Score, Abbreviated Injury Scale (AIS) score of different body regions and comorbidities. Excluded from the study were all patients who were not tested for cannabis or tested for cannabis but were also tested positive for alcohol and other drugs and those suffering from mental conditions. Propensity matched analysis was performed. The outcome of interest was overall in-hospital mortality and complications.

RESULTS

Propensity matched analysis created 28,028 pairs. The analysis showed no significant difference in-hospital mortality between cannabis positive and cannabis negative groups (3.2% vs. 3.2%). The median length of hospital stay in both groups was not significantly different (4 [IQR: 3-8] vs. 4 [IQR: 2-8] days). No significant difference was found between the two groups regarding hospital complications except in pulmonary embolism (PE) with 0.1% less incidence of PE in the cannabis positive group compared to the cannabis negative group (0.4 vs. 0.5%). The incidence of DVT was identical in both groups (0.9% vs. 0.9%).

CONCLUSION

Cannabis was not associated with overall in-hospital mortality or morbidity. There was a slight decrease in the incidence of PE in the cannabis positive group.

Cannabis and tobacco use among adolescents aged 12-17 years from 16 low- and middle-income countries

Background

We aimed to examine the association between cannabis use and tobacco use in 12-17-year-old adolescents residing in low- and middle-income countries (LMICs).

Methods

We used data from the Global School-based Student Health Survey collected between 2012 and 2022. We selected 16 LMICs based on pre-defined inclusion criteria and compared the prevalence of cannabis use for female and for male adolescents for each country. We estimated age- and sex-standardised distributions of tobacco use, school truancy, suicide attempt, sex with multiple partners, physical fighting, perceived school kindness, and parental monitoring were estimated. We used multivariable logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) measuring associations between cannabis use and other variables. We generated pooled estimates through random effects meta-analyses.

Results

The overall pooled prevalence of cannabis use was 4.3% (95% CI = 3.2-5.9), with significant between-country heterogeneities (I² = 91.4%; P = 0.000). Cannabis use was more prevalent in males than in females in each country. Tobacco use was strongly associated with cannabis use in all 16 LMICs. Tobacco users had approximately 11 to 14 times greater odds of cannabis use than non-tobacco users. Sex with multiple partners, suicide attempts, and school truancy had a robust association with cannabis use in over half of LMICs.

Conclusions

There is a need for comprehensive preventive measures targeting multiple risk behaviours associated with cannabis use for adolescents in LMICs.

Cannabis Use and Symptomatic Relapse in First Episode Schizophrenia: Trigger or Consequence? Data From the OPTIMISE Study

BACKGROUND AND HYPOTHESIS

This analysis examined the relationship between cannabis use, compliance with antipsychotics and risk for relapse in patients in remission following a first episode of schizophrenia, schizophreniform, or schizoaffective disorder.

STUDY DESIGN

Analyses were performed on data from a large European study on first episode of schizophrenia, schizophreniform, or schizoaffective disorder (OPTiMiSE). After 10 weeks of antipsychotic treatment, 282/446 patients (63%) met criteria for symptomatic remission; of whom 134/282 (47.5%) then completed a 1-year follow-up. Cross-lagged models and mediation models investigated the temporal relationships between cannabis use, compliance with antipsychotics, social functioning, and symptomatic worsening/relapse.

STUDY RESULTS

Compared to nonusers, cannabis use increased risk for relapse, adjusted hazard ratio (HR) = 3.03 (SE = 0.32), P < .001, even in patients who were compliant with antipsychotic medication, adjusted HR = 2.89, (SE = 0.32), P < .001. Cannabis use preceded symptomatic worsening and was followed by worsening of Positive and Negative Syndrome Scale total score at the 1-year end-point (standardized β = 0.62, SE = 0.19, P = .001) and by worsening of social functioning (coef = -0.66, P ≤ .001).

CONCLUSIONS

In patients in remission from their first episode of schizophrenia, schizophreniform, or schizoaffective disorder, cannabis use increases the rate of relapse in both compliant and noncompliant individuals. Importantly, the temporal relationship between cannabis and relapse was that cannabis use preceded later relapse, noncompliance, and decrease in social functioning, and not that patients began to relapse, then used cannabis. Further research with a precision psychiatry approach might identify those patients in particular danger of relapse when using cannabis.

Nondisordered Cannabis Use Among US Adolescents

Importance

Cannabis use is increasingly viewed by adolescents as not harmful. Youths with cannabis use disorder (CUD) are recognized by clinicians as being at risk for adverse outcomes, yet little is known about the associations between subclinical cannabis use (ie, nondisordered cannabis use [NDCU]) and adverse psychosocial events.

Objective

To describe the prevalence and demographics of NDCU and to compare associations of cannabis use with adverse psychosocial events among adolescents with no cannabis use, NDCU, and CUD.

Design, Setting, and Participants

This cross-sectional study used a nationally representative sample derived from the 2015 to 2019 National Survey on Drug Use and Health. Participants were adolescents aged 12 to 17 years, separated into 3 distinct groups: nonuse (no recent cannabis use), NDCU (recent cannabis use below diagnostic threshold), and CUD. Analysis was conducted from January to May 2022.

Exposures

CUD, NDCU, or cannabis nonuse. NDCU was defined as endorsing recent cannabis use but not meeting the Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) (DSM-5) CUD criteria. CUD was defined using DSM-5 criteria.

Main Outcomes and Measures

The main outcomes were prevalence of adolescents meeting criteria for NDCU and associations between adverse psychosocial events and NDCU, adjusted for sociodemographic characteristics.

Results

The 68 263 respondents (mean [SD] age, 14.5 [1.7] years; 34 773 [50.9%] males) included in the analysis represented an estimated yearly mean of 25 million US adolescents during 2015 to 2019. Among respondents, 1675 adolescents (2.5%) had CUD, 6971 adolescents (10.2%) had NDCU, and 59 617 adolescents (87.3%) reported nonuse. Compared with nonusers, individuals with NDCU had approximately 2 to 4 times greater odds of all adverse psychosocial events examined, including major depression (adjusted odds ratio [aOR], 1.86; 95% CI, 1.67-2.08), suicidal ideation (aOR, 2.08; 95% CI, 1.88-2.29), slower thoughts (aOR, 1.76; 95% CI, 1.58-1.96), difficulty concentrating (aOR, 1.81; 95% CI, 1.65-2.00), truancy (aOR, 1.90; 95% CI, 1.67-2.16), low grade point average (aOR, 1.80; 95% CI, 1.62-2.00), arrest (aOR, 4.15; 95% CI, 3.17-5.43), fighting (aOR, 2.04; 95% CI, 1.80-2.31), and aggression (aOR, 2.16; 95% CI, 1.79-2.62). Prevalence of adverse psychosocial events was greatest for adolescents with CUD (range, 12.6% to 41.9%), followed by NDCU (range, 5.2% to 30.4%), then nonuse (range, 0.8% to 17.3%).

Conclusions and Relevance

In this cross-sectional study of US adolescents, past-year NDCU was approximately 4 times as prevalent as past-year CUD. A stepwise gradient association was observed for odds of adverse psychosocial events between adolescent NDCU and CUD. In the context of US normalization of cannabis use, prospective research into NDCU is necessary.

Association Between Cannabis and Violence in Community-Dwelling Patients With Severe Mental Disorders: A Cross-sectional Study Using Machine Learning

The objective of this cross-sectional study was to identify cannabis-related features and other characteristics predictive of violence using a data-driven approach in patients with severe mental disorders (SMDs). A Least Absolute Shrinkage and Selection Operator regularization regression model was used on the database consisting of 97 patients with SMD who completed questionnaires measuring substance use and violence. Cannabis use, particularly related to patients' decision to consume or time spent using, was a key predictor associated with violence. Other patterns of substance use and personality traits were identified as strong predictors. Regular patterns of cannabis use and interpersonal issues related to cannabis/stimulant abuse were inversely correlated to violence. This study identified the effect of several predictors correlated to violence in patients with SMD using a regularization regression model. Findings open the door to better identify the profiles of patients that may be more susceptible to perpetrate violent behaviors.

Illicit drug use and violence

This chapter reviews evidence on the relationship between illicit drug use and violence, specifically cannabis, stimulant drugs, and opioids. It summarizes findings of systematic reviews of evidence on cannabis, stimulant drugs, and opioids. It also examines evidence from epidemiological studies of drug use among violent offenders and of violence among persons who use drugs, intervention studies, animal studies, human laboratory studies, and human neuroimaging studies. More studies have examined cannabis because of its higher prevalence of use. There is an association between cannabis use and violence, suggestive evidence of a dose-response relationship between the frequency of cannabis use and violence, and a stronger association in persons with psychoses. There is similar emerging evidence on stimulant use and violence, but evidence on opioids is very limited. There is limited and mixed evidence from intervention studies that reducing drug use reduces violence. Animal and human studies provide potential biological explanations for these associations. The association between cannabis use and violence is most consistent but limited by study heterogeneity and lack of control for potential confounders. It is unclear whether these associations are causal or reflect reverse causation or the effects of confounding.

A Six-Year Follow-up of People Who Use Cannabis in Iran - A Case Series

BACKGROUND

Frequent cannabis use is associated with adverse health-related outcomes. This study followed up individuals who used cannabis to assess their use and adverse event status.

METHODS

The eligible individuals, recruited in the Iranian Mental Health Survey (IranMHS), were contacted via telephone calls six years after the index interview. The frequency of cannabis use and the occurrence of selected adverse events were recorded. The baseline status was extracted from the index survey. If any individual was inaccessible, his/her vital status was assessed.

FINDINGS

Of the 50 eligible individuals (all male), two had died. Moreover, from among 25 reached participants, 19 reported abstinence from cannabis in the past year, and 18 reported at least one adverse event in the past six years. Violence and imprisonment were the most common events reported.

CONCLUSION

Six years after the index interview, most of the participants abstained from cannabis. Besides, adverse events were common, emphasizing the need for further investigations on larger samples of cannabis users.

Adolescent Cannabis Use, Comorbid Attention-Deficit/Hyperactivity Disorder, and Other Internalizing and Externalizing Disorders

Cannabis use often co-occurs with attention-deficit/hyperactivity disorder and other internalizing and externalizing disorders. Treatment planning, including pharmacologic and psychosocial interventions, for these comorbid disorders require thorough diagnostic evaluation to determine the extent of social, emotional, and behavioral impairments, severity of substance use, and motivation for change. Improved understanding of these comorbid disorders will inform treatment planning that address current symptoms and behaviors and may also prevent the development of mental health and substance use disorders in early adulthood.

Harm Reduction Strategies among University Students Who Use Alcohol and Cannabis, and Related Psychological Variables: A Systematic Review

This systematic review identifies the psychological variables associated with the use of harm reduction strategies (HRS) among university students who use alcohol or cannabis. The reviewed studies are categorized according to the psychological variables studied and the different analytic approaches used (direct effects, mediation, and moderation). Among the empirical peer-reviewed studies identified (n = 76), most (94.7%) were cross-sectional studies conducted in the US (90.8%) with samples of alcohol-using university students (86.8%). Five categories were identified: mental health, motives/expectancies, personality, social cognition, and self-efficacy. The most studied constructs were motives, anxiety and depression, impulsivity, and social norms. Most studies conducted mediation or moderation analyses including psychological variables, HRS and alcohol outcomes. Social, enhancement and coping motives, impulsivity, and social norms of alcohol use were associated with lower use of HRS, which, in turn, was associated with a higher number of alcohol/cannabis outcomes. The results of moderation studies consistently suggest that HRS use was more protective for students with poor mental health, high impulsivity, and low self-regulation. The synthesis of evidence provided in this review could be useful for guiding future research and informing the design of interventions aimed at promoting the use of HRS among university students who use alcohol and/or cannabis.

Violent Behaviours among Adolescents and Young Adults: Association with Psychoactive Substance Use and Parenting Styles

This study extends existing research on the relationship between psychoactive substance use among young people and violent behaviour, by evaluating the possible effect of the modification of parenting in a nationally representative sample of 14,685 Italian students drawn from the 2019 wave of the ESPAD Italia survey (51% male; mean age about 17 years). Parental dimensions considered in the study were rule-setting, monitoring, and emotional support, as well as the possible absence of a parent. Relative risk ratios and binary logistic regressions were used to estimate the associations separately for adolescents (15–17) and young adults (18–19). Overall, parental rule-setting, perceived parental monitoring, and emotional support were protective factors for substance use, and the strength of this relationship increased with the frequency of use. Among adolescents, the absence of a parent represented a risk factor. In both age groups, the odds of engaging in violent behaviour was increased among those reporting alcohol intoxication and substance use and the greater the frequency of use, the greater the increase in the odds. As parental monitoring and emotional support decreased, the odds of engaging in violent behaviour increased (except in the case of lower parental support among young adults), while the opposite applies to parental rule-setting. The odds of engaging in violent behaviour were increased among those reporting the absence of a parent only in the adolescent age group. Parental rule-setting was found to have an effect only among adolescents, increasing the odds of violent behaviour among frequent drinkers. Our results might be helpful to signal adolescents who would be more prone to adopt violent behaviour in order to target prevention policies.

Conceptualizing and considering Cannabis-Related "Harm-to-Others": The Role of Cannabis-Related Violence

Public health-oriented frameworks for cannabis use of control, including legalization, are evolving. Most frameworks aim to reduce cannabis-related health harms that materialize among users; there has been comparably limited focus on cannabis-related "harm-to-others". A longstanding issue for other psychoactive substances, and increasingly recognized form of cannabis-related harm-to-others involves violence/aggression. We briefly review relevant epidemiological and psycho-behavioral data related to cannabis-related violence and aggression, and discuss intervention prospects. Systematic review and other study data show a moderately positive association between cannabis use and perpetration of physical (including intimate-partner) violence, for example involving assault, aggression, and fighting; this risk may be further elevated by intensive use patterns. Such harms may involve injuries/deaths and contribute to the cannabis-related burden of disease. Within the contexts of public health-oriented frameworks for cannabis control, greater awareness and targeted interventions regarding the risk for exposure to violence related to cannabis use should be promoted in addition to protections for users' health.

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

INTRODUCTION

Recently, the literature has shown that Cannabis Use (CU) was a risk factor for Violent Behavior (VB) in patients with psychosis, and those in the early phase of psychosis (EPP). These findings are relevant because of the high prevalence of CU in this EPP, and the potential for prevention during this phase of illness. However, there is still a lack of clear explanations, supported by empirical evidence, about what underlies the link between CU and VB against other.

METHOD

This viewpoint reviews the scientific literature on the link between CU and VB, and the involvement of impulsivity in this relationship. This last point will be addressed at clinical and neurobiological levels.

RESULTS

Recent studies confirmed that CU is particularly high in the EPP, and is a risk factor for VB in the EPP and schizophrenia. Studies have also shown that impulsivity is a risk factor for VB in psychosis, is associated with CU, and may mediate the link between CU and VB. Research suggests a neurobiological mechanism, as CU affects the structures and function of frontal areas, known to play a role in impulsive behavior.

CONCLUSION

Scientific evidence support the hypothesis of an involvement of impulsivity as a variable that could mediate the link between CU and aggression, particularly, when CU has an early onset. However, this hypothesis should be confirmed with longitudinal studies and by taking into account confounding factors. The studies highlight the relevance of early prevention in the EPP, in addition to interventions focusing on psychotic disorders.

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

Importance

State cannabis laws are changing rapidly. Research is inconclusive about their association with rates of self-harm and assault. Existing studies have not considered variations in cannabis commercialization across states over time.

Objective

To evaluate the association of state medical and recreational cannabis laws with self-harm and assault, overall and by age and sex, while considering varying degrees of commercialization.

Design, Setting, and Participants

Using a cohort design with panel fixed-effects analysis, within-state changes in claims for self-harm and assault injuries before and after changes in cannabis laws were quantified in all 50 US states and the District of Columbia. Comprehensive claims data on commercial and Medicare Advantage health plan beneficiaries from January 1, 2003, to December 31, 2017, grouped by state and month, were evaluated. Data analysis was conducted from January 31, 2020, to January 21, 2021.

Exposures

Categorical variable that indexed the degree of cannabis legalization in each state and month based on law type (medical or recreational) and operational status of dispensaries (commercialization).

Main Outcomes and Measures

Claims for self-harm and assault injuries based on International Classification of Diseases codes.

Results

The analysis included 75 395 344 beneficiaries (mean [SD] age, 47 [22] years; 50% female; and median follow-up, 17 months [interquartile range, 8-36 months]). During the study period, 29 states permitted use of medical cannabis and 11 permitted recreational cannabis. Point estimates for populationwide rates of self-harm and assault injuries were higher in states legalizing recreational cannabis compared with states with no cannabis laws, but these results were not statistically significant (adjusted rate ratio [aRR] assault, recreational dispensaries: 1.27; 95% CI, 0.79-2.03;self-harm, recreational dispensaries aRR: 1.15; 95% CI, 0.89-1.50). Results varied by age and sex with no associations found except for states with recreational policies and self-harm among males younger than 40 years (aRR <21 years, recreational without dispensaries: 1.70; 95% CI, 1.11-2.61; aRR aged 21-39 years, recreational dispensaries: 1.46; 95% CI, 1.01-2.12). Medical cannabis was generally not associated with self-harm or assault injuries populationwide or among age and sex subgroups.

Conclusions and Relevance

Recreational cannabis legalization appears to be associated with relative increases in rates of claims for self-harm among male health plan beneficiaries younger than 40 years. There was no association between cannabis legalization and self-harm or assault, for any other age and sex group or for medical cannabis. States that legalize but still constrain commercialization may be better positioned to protect younger male populations from unintended harms.

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

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 cannabis-related 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 two-fold: (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.