Early onset of cannabis use and violent behavior in psychosis

Abstract

Background: Although evidence from psychosis patients demonstrates the adverse effects of cannabis use (CU) at a young age and that the rate of CU is high in subgroups of young violent patients with psychotic disorders, little is known about the possible effect of the age of onset of CU on later violent behaviors (VB). So, we aimed to explore the impact of age at onset of CU on the risk of displaying VB in a cohort of early psychosis patients. Method: Data were collected prospectively over a 36-month period in the context of an early psychosis cohort study. A total of 265 patients, aged 18–35 years, were included in the study. Logistic regression was performed to assess the link between age of onset of substance use and VB. Results: Among the 265 patients, 72 had displayed VB and 193 had not. While violent patients began using cannabis on average at age 15.29 (0.45), nonviolent patients had started on average at age 16.97 (0.35) (p = 0.004). Early-onset CU (up to age 15) was a risk factor for VB (odds ratio = 4.47, confidence interval [CI]: 1.13–20.06) when the model was adjusted for age group, other types of substance use, being a user or a nonuser and various violence risk factors and covariates. History of violence and early CU (until 15) were the two main risk factors for VB. Conclusions: Our results suggest that early-onset CU may play a role in the emergence of VB in early psychosis.

Aggressive Behavior and Psychiatric Inpatients: a Narrative Review of the Literature with a Focus on the European Experience

“…On this line, a recent Swiss cohort study on an early psychosis population of 265 patients found that the earlier the cannabis abuse started, the higher was the risk of physical aggressiveness [99].…”

“…Cannabis abuse has been confirmed as a risk factor for violence in a Swiss investigation on patients with early psychosis. The combination of cannabis use, impulsivity, lack of insight, and non-adherence to treatment furtherly increased the risk [99].…”

Aggressive behaviour in antipsychotic‐naive first‐episode schizophrenia patients, their unaffected siblings and healthy controls

“…A three‐step hierarchical multiple regression analysis was then performed to identify the most important clinical covariates of aggression scores in the patients group. Alcohol and cannabis use (Kudumija Slijepcevic et al, 2014; Moulin et al, 2020; Oueslati et al, 2018), as well as other factors including DUP, insight and psychotic symptoms (Nielssen et al, 2012) have been shown to be strongly associated with aggression and violence in patients with psychotic disorders, and were thus added as covariates. For this, aggression scores were taken as a dependent variable and other variables (age, gender, alcohol and cannabis use, age of onset of illness, DUP, functioning, psychopathology, insight, impulsiveness and psychopathy) were used as independent variables.…”

“…Indeed, patients with schizophrenia who report substance use have a confirmed increased risk of aggression (Faay & Sommer, 2021). Particularly, alcohol (Kudumija Slijepcevic et al, 2014) and cannabis (Moulin et al, 2020) have been shown to be among the strongest predictors of violent behaviours in schizophrenia. Furthermore, multiple clinical risk factors have been reported, such as a younger age at illness onset, more severe psychotic symptomatology (Caqueo‐Urízar et al, 2016), and a longer duration of untreated psychosis (Rund, 2018).…”

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

“…It seems also that dose-response ( 39 , 46 , 60 , 61 ), trajectory of consumption ( 56 ), and persistence of CU ( 39 ) could be important variables in the association between CU and VB. In studies conducted in prisoners ( 53 ) and in the general population ( 61 ), it has been shown that the average age at which the violent patients started using cannabis was 15 years [two years earlier than the non-violent patient group ( 62 )], and that the precocity of CU was a risk factor for VB ( 62 ) .…”