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Person-specific processes contribute to link between cannabis use, psychotic-like experiences

Nicole R. Karcher

Although the link between frequent and problem cannabis use and psychotic-like experiences primarily involves genetic overlap, individual-specific pathways appear to also play a role, according to an analysis published in JAMA Psychiatry.

“Understanding the nature of the relationship between psychotic-like experiences and cannabis use has critical current importance, as cannabis is increasingly becoming legally available (in the U.S.) for both medicinal and recreational purposes,” Nicole R. Karcher, PhD, of the department of psychiatry, Washington University, told Healio Psychiatry.

“The majority of previous research has focused on the association with cannabis use in psychotic disorder populations (eg, schizophrenia),” she continued. “However, it is important to understand this association in psychotic-like experiences given the greater prevalence of psychotic-like experiences ... compared to psychotic disorders.”

Researchers collected diagnostic interviews and self-reported data from two population-based samples of twin and nontwin sibling pairs — 1,188 participants from the Human Connectome Project and 3,486 from Australian Twin Registry Cohort 3 — in this cross-sectional analysis.

Using the Semi-structured Assessment for the Genetics of Alcoholism, the investigators measured participants’ frequent cannabis use (100 times or more), DSM-IV lifetime cannabis use disorder diagnosis and current cannabis use. To estimate the genetic and environmental correlations, Karcher and colleagues analyzed the variance in and covariance between each cannabis involvement measure and psychotic-like experiences into additive genetic, shared environmental and individual-specific environmental sources.

Analysis revealed psychotic-like experiences were linked to frequent cannabis use (beta = 0.11; 95% CI, 0.08-0.14), cannabis use disorder (beta = 0.13; 95% CI, 0.09-0.16) and current cannabis use (beta = 0.07; 95% CI, 0.04-0.1). Participants reporting frequent use, cannabis use disorder and current use were 1.21 to 1.26 times more likely to have at least one psychotic-like experience than those who used cannabis to a lesser extent or not at all, according to the study. These associations remained after adjusting for covariates.

Cannabis involvement and psychotic-like experiences were heritable; the researchers found that genetic factors accounted for 69.2% to 84.1% of the observed connection, with the remainder of covariance explained by individual-specific environmental factors.

Psychotic-like experiences were more common in cannabis-exposed members of discordant pairs of twins/siblings compared with their relative who used cannabis to a lesser degree (P < .05). These findings suggested that, even within twin and nontwin sibling pairs, all cannabis-involvement variables contributed to more frequent reports of psychotic-like experiences.

“Overall, the current study helps clarify the relationship between cannabis use and psychotic-like experiences, indicating that while the association primarily consists of shared genetic factors, there is an alterable individual-specific component,” Karcher told Healio Psychiatry. “This suggests that targeting cannabis use prevention may be an important tool in preventing exacerbation of psychotic-like experiences in individuals at increased genetic liability.”

“For clinicians, preventing or reducing frequent and problematic cannabis use in individuals experiencing psychotic-like experiences may be one targeted intervention approach,” she said. – by Savannah Demko

Disclosure: Karcher reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.