This article is more than 5 years old. Information may no longer be current.

Continued cannabis use increases risk for psychosis relapse

Recent findings indicated an increased risk for psychosis relapse among individuals with first-episode psychosis who continued to use cannabis.

“Understanding the nature of the association between cannabis use and psychotic disorders is crucial for the formulation of evidence-based health policies concerning cannabis, especially in light of changing public attitudes and legalization of cannabis use in several states in the United States and other countries,” Tabea Schoeler, MSc, a research student at King’s College London, and colleagues wrote. “This understanding is particularly important because psychotic disorders, such as schizophrenia, cause the most severe health loss of all human disorders and are associated with considerable financial burden. Psychotic disorders are also associated with a high rate of comorbid abuse of cannabis, the most commonly used illicit drug worldwide.”

To assess associations between continued cannabis use after onset of psychosis and risk for relapse of psychosis, researchers conducted a prospective cohort study of 220 individuals with first-episode psychosis and followed them for at least 2 years after onset of psychosis. Study participants had a mean age of 28.62 years.

Fixed-effects models adjusted for time-variant and time-invariant unobserved confounders indicated an increased risk for psychosis relapse during periods of cannabis use (OR = 1.13; 95% CI, 1.03-1.24), compared with periods of no cannabis use.

Change in the pattern of continuation significantly increased risk for psychosis relapse (OR = 1.07; 95% CI, 1.02-1.13), suggesting a dose-dependent association, according to researchers.

The association between continued cannabis use and risk for psychosis relapse indicated an effect of cannabis use on subsequent risk for relapse (P = .04) and not an effect of relapse on subsequent cannabis use (P = .59), according to cross-lagged analysis.

“Together, these results suggest that it is more likely than not that continued cannabis use after onset of psychosis is causally associated with increased risk of relapse of psychosis, resulting in psychiatric hospitalization. Because cannabis use is a potentially modifiable risk factor that has an adverse influence on the risk of relapse of psychosis and hospitalization in a given individual, with limited efficacy of existing interventions, these results underscore the importance of developing novel intervention strategies and demand urgent attention from clinicians and health care policymakers,” the researchers concluded. – by Amanda Oldt

Disclosure: Schoeler reports no relevant financial disclosures. Please see the study for a full list of relevant financial disclosures.