Adolescent cannabis initiation linked to increased psychosis spectrum symptoms | Image Credit: © hanohiki - © hanohiki - stock.adobe.com.

Investigators of a recent study published in JAMA Psychiatry found that adolescents who used cannabis ended up reporting a greater number of psychosis spectrum symptoms and more distress compared to those who never used cannabis.

Background

According to the study investigators, led by Juston Osborne, PhD, of the Department of Psychiatry at Washington University in St. Louis, Missouri, cannabis use in adolescence has been consistently posited to contribute to the onset and progression of psychosis. Cannabis use can lead to a 2- to 4-fold increased risk of psychosis compared to those who never have used cannabis, the authors noted.

"Cannabis initiation in early adolescence has been associated with earlier onset of psychotic disorders, more severe symptoms, and greater likelihood of symptom relapse among those who develop psychosis," wrote Osborne and colleagues. "Cannabis is the most frequently used illicit substance among adolescents, and this trend is increasing (from 11% to 22% over the past 2 decades) alongside a decrease in its perceived risk of harm among adolescents (from 36.3% to 25% for weekly use)."

To better understand the association between adolescent cannabis initiation and psychosis spectrum symptomology, the study authors sought to test a trio of hypotheses that could explain this association and symptom trajectories across adolescent development (10 to 15 years of age). Hypotheses included contributing risk, shared vulnerability, and self-medication, with author explanation below:

Contributing risk hypothesis - Adolescent cannabis use may causally contribute to the emergence of psychosis via the disruption of normative neurodevelopmental processes

Shared vulnerability hypothesis - Postulates that genetic, gestational, or environmental factors may confer vulnerability for both cannabis use and psychosis

Self-medication hypothesis - suggests that individuals may initiate cannabis use in an attempt to alleviate psychosis spectrum and secondary symptoms, such as anxiety and dysphoria, reflecting an effort to self-medicate by affected individuals

When evaluating the contributing risk hypothesis, investigators tested whether psychosis spectrum symptoms increased after cannabis initiation. For the shared vulnerability hypothesis, whether psychosis spectrum symptoms differed between those who used cannabis and those who did not was tested. Lastly, to evaluate self-medication hypothesis, investigators tested whether psychosis spectrum symptoms increased leading up to cannabis use initiation.

Study details and results

Using data from the Adolescent Brain Cognitive Development (ABCD) Study—an ongoing large-scale, longitudinal study of brain development and mental and physical health of children in the United States—data were collected from 21 research sites and included 11,868 adolescents aged 9 to 10 years at baseline. The authors used discontinuous growth curve modeling to assess trajectories of psychosis spectrum symptoms before and after cannabis initiation.

Mean age of the participants were 9.5 years and 52% were male. Results demonstrated that those who used cannabis at any point during the study period reported increased psychosis spectrum symptoms (B, 0.86; 95% CI, 0.68-1.04) and more distress (B, 1.17; 95% CI, 0.96-1.39), compared to those who never used cannabis.

The number of psychosis symptoms (B, 0.16; 95% CI, 0.12-0.20) and distress (B, 0.23; 95% CI, 0.21-0.26) from psychosis spectrum symptoms increased in the time leading up to cannabis initiation, which was consistent with the self-medication hypothesis.

Conclusion

"In sum, the current research provides support for the shared vulnerability and self-medication explanations for associations between cannabis use and psychosis risk," the study authors concluded. "More research following up with individuals for a longer period after cannabis initiation is needed to provide a diagnostic test of the contributing risk hypothesis."

Reference:

Osborne KJ, Barch DM, Jackson JJ, Karcher NR. Psychosis Spectrum Symptoms Before and After Adolescent Cannabis Use Initiation. JAMA Psychiatry. Published online November 06, 2024. doi:10.1001/jamapsychiatry.2024.3525