Persistency Of Cannabis Use Predicts Violence Following Acute Psychiatric Discharge



Violence is a major concern and is prevalent across several mental disorders. The use of substances has been associated with an exacerbation of psychiatric symptoms as well as with violence. Compared to other substances such as alcohol and cocaine, existing literature on the cannabis-violence relationship has been more limited, with most studies being conducted in the general population, and has shown controversial results. Evidence has suggested a stronger relationship when examining the effects of the persistency of cannabis use on future violent behaviors. Though, while cannabis use is highly prevalent amid psychiatric patients, far less literature on the subject has been conducted in this population. Hence, the present prospective study aims to investigate the persistency of cannabis use in psychiatric patients.


The sample comprised of 1,136 recently discharged psychiatric patients provided by the MacArthur Risk Assessment Study. A multi-wave (five-assessment) follow-up design was employed to allow temporal sequencing between substance use and violent behaviors. Generalized estimating equations (GEE) were used to examine the effect of persistency of cannabis use on violence, while controlling for potential confounding factors. Potential bidirectional association was also investigated using the same statistical approach.


Our results suggest a unidirectional association between cannabis use and violence. GEE model revealed that the continuity of cannabis use across more than one time wave was associated with increased risks of future violent behavior. Patients who reported having used cannabis at each follow-up periods were 2.44 times more likely to display violent behaviors (OR = 2.44, 95% CI: 1.06-5.63, p < 0.05).

Odds ratios for violent behaviors associated with substance use across each time points. x-Axis represent the number of follow-up periods with substance-use, y-axis represent the Odds Ratios; Reference is no use of substance across time points; Odds Ratios are controlled for the effects of time, other substances used at each time point, age, age at first hospitalization, sex, ethnicity, Schizophrenia-Spectrum disorders (presence/absence), affective disorders (presence/absence), psychopathic traits (PCL), impulsivity (BIS-11) (*p < 0.05; **p < 0.01; ***p < 0.001; N.S., Not statistically significant).


These findings are particularly relevant as they suggest that the longer individuals report having used cannabis after a psychiatric discharge, the more likely they are of being violent in the following time waves. These results add to our understanding of the negative consequences of chronic cannabis use amid psychiatric patients.

Source: September 2017

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