Brief report: changes in brain function during acute cannabis intoxication: preliminary findings suggest a mechanism for cannabis-induced violence

The Impact of Recreational Marijuana Legalization on Simple Assault in Oregon

There has been heightened public concern about the implications of recreational marijuana legalization to public safety. Prior research on this issue has primarily focused on Colorado and Washington State-the two states that first legalized recreational marijuana in the U.S.-and on legalization's impact on major crimes. This study extends this line of research to Oregon (OR, legalized in late 2014) and examines the impact of legalization on a less serious form of violent crime-simple assault. Using Uniform Crime Reporting (UCR) Program data from 2007 to 2017 and a quasi-experimental research design, this study found that counties in OR have experienced increases in simple assault rate following legalization, relative to rates in the 19 non-legalized states. Findings suggest the need for more scholarly efforts to explore the potential impact of marijuana legalization on different subtypes of violent crime in other legalized states.

Effects of recreational marijuana legalization on clearance rates for violent crimes: Evidence from Oregon

One important public concern about the impact of recreational marijuana legalization is how legalization may affect police performance in solving serious crimes. Based on Uniform Crime Reports (UCR) data from 2007 to 2017, this study used difference-in-differences (DID) analysis and the synthetic control method (SCM) to examine the effect of recreational marijuana legalization on the clearance rates for multiple types of violent crimes in Oregon (OR), a state that legalized recreational marijuana in late 2014. Results offer some evidence suggesting a beneficial impact of legalization on violent crime clearances, as manifested by significant increases in the clearance rate for overall violent crimes and that for aggravated assault in OR counties relative to those in the non-legalized states following legalization. Results also demonstrate that the positive effect of legalization on violent crime clearance rates appears to reduce over time.

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

OBJECTIVE

The aim of this meta-analysis was to investigate the extent to which cannabis use among youths is associated with the risk of perpetrating physical violence.

METHODS

Searches were conducted in PubMed, PsycINFO, Web of Science, and Google Scholar for articles published from the inception of each database to July 2019. All studies that examined both cannabis use and the perpetration of physical violence in a sample of youths and young adults <30 years old were included. The meta-analysis was performed with a random-effects model. Risk of publication bias was assessed with Egger's test. Guidelines from the Meta-Analysis of Observational Studies in Epidemiology were followed.

RESULTS

After screening 11,348 potential studies, 30 study arms were included, yielding a total of 296,815 adolescents and young adults. The odds ratio for the pooled studies was 2.11 (95% CI=1.64, 2.72). The pooled odds ratios were 2.15 (95% CI=1.58, 2.94) and 2.02 (95% CI=1.26, 3.23) for the cross-sectional and longitudinal studies, respectively. Preliminary evidence suggests that the risk of violence was higher for persistent heavy users (odds ratio=2.81, 95% CI=1.68, 4.74) compared with past-year users (odds ratio=2.05, 95% CI=1.5, 2.8) and lifetime users (odds ratio=1.94, 95% CI=1.29, 2.93). The odds ratio for unadjusted studies was 2.62 (95% CI=1.89, 3.62), and for studies using odds ratios adjusted for potential confounding factors, 2.01 (95% CI=1.57, 2.56).

CONCLUSIONS

These results demonstrate a moderate association between cannabis use and physical violence, which remained significant regardless of study design and adjustment for confounding factors (i.e., socioeconomic factors, other substance use). Cannabis use in this population is a risk factor for violence.

Subjective aggression during alcohol and cannabis intoxication before and after aggression exposure

RATIONALE

Alcohol and cannabis use have been implicated in aggression. Alcohol consumption is known to facilitate aggression, whereas a causal link between cannabis and aggression has not been clearly demonstrated.

OBJECTIVES

This study investigated the acute effects of alcohol and cannabis on subjective aggression in alcohol and cannabis users, respectively, following aggression exposure. Drug-free controls served as a reference. It was hypothesized that aggression exposure would increase subjective aggression in alcohol users during alcohol intoxication, whereas it was expected to decrease subjective aggression in cannabis users during cannabis intoxication.

METHODS

Heavy alcohol (n = 20) and regular cannabis users (n = 21), and controls (n = 20) were included in a mixed factorial study. Alcohol and cannabis users received single doses of alcohol and placebo or cannabis and placebo, respectively. Subjective aggression was assessed before and after aggression exposure consisting of administrations of the point-subtraction aggression paradigm (PSAP) and the single category implicit association test (SC-IAT). Testosterone and cortisol levels in response to alcohol/cannabis treatment and aggression exposure were recorded as secondary outcome measures.

RESULTS

Subjective aggression significantly increased following aggression exposure in all groups while being sober. Alcohol intoxication increased subjective aggression whereas cannabis decreased the subjective aggression following aggression exposure. Aggressive responses during the PSAP increased following alcohol and decreased following cannabis relative to placebo. Changes in aggressive feeling or response were not correlated to the neuroendocrine response to treatments.

CONCLUSIONS

It is concluded that alcohol facilitates feelings of aggression whereas cannabis diminishes aggressive feelings in heavy alcohol and regular cannabis users, respectively.

Does marijuana use lead to aggression and violent behavior?

Marijuana use and violent behavior are causing widespread public concern. This article reviews theory and research on the relation between marijuana use and aggressive/violent behavior. It is evident from the inconsistent findings in the literature that the exact nature of the relation remains unclear. This article identifies several possible reasons for these contradictory findings and provides suggestions for future research. In particular, more research is needed on the different subtypes of aggressive behavior. Further research is also needed to elucidate the associations between gender, marijuana use, and violent behavior. Likewise, an important task for future research is to continue to tease apart the complex relations between gang involvement, marijuana use, and violent behavior. Longitudinal studies also warrant further investigation. Moreover, future research should control for several potentially confounding variables.

Clinical and cognitive associations with aggression in the first episode of psychosis

OBJECTIVE

Although there may be an increased risk of aggression in first-episode psychosis, little is known about the clinical and cognitive associations of serious and less serious aggression during this phase of psychotic illness.

METHODS

Eighty-five patients in the first episode of psychosis under the age of 26 underwent comprehensive clinical assessment and cognitive testing. Aggression was assessed using a purpose-designed rating scale based on corroborative interviews to record 10 types of aggressive behaviour in the 3 months before presenting for treatment.

RESULTS

Thirty-seven of 85 patients (43.5%) exhibited physically aggressive behaviour and 23 patients (27.1%) had assaulted another person or used a weapon. Young age and elevated scores in the mania rating scale were associated with a history of any type of aggression. Serious aggression was associated with regular cannabis use and more errors of commission on a continuous performance task.

CONCLUSIONS

The clinical features associated with less serious aggression were different to those associated with more serious forms of aggression. Serious aggression is associated with regular cannabis use and also reduced behavioural inhibition. Awareness of substance use and neurocognitive deficits may assist in the identification of potentially violent patients.

The effect of cannabis on the brain: can it cause brain anomalies that lead to increased risk for schizophrenia?

PURPOSE OF REVIEW

This review explores what is known about the association of cannabis with schizophrenia, its effects on the brain, and whether the brain changes known to be present in schizophrenia could be caused by cannabis and thus lead to a psychosis.

RECENT FINDINGS

The heavy use of cannabis is known to be associated with some adverse consequences, such as the occurrence of acute psychotic episodes and the development of chronic schizophrenia in some people even after its use has terminated. Recent studies have produced controversy about whether cannabis in heavy use can cause irreversible brain damage, particularly to adolescents, and thus whether a chronic psychosis could be a result of brain changes caused by cannabis.

SUMMARY

From the evidence that exists, it appears that the above view is unlikely and that cannabis may even have benign effects on brain structure, not producing deleterious damage. Its neurochemical interactions with the dopaminergic pathway, however, may, particularly in genetically vulnerable individuals, have adverse consequences.