Concurrent and Sustained Cumulative Effects of Adolescent Marijuana Use on Subclinical Psychotic Symptoms

Abstract

Objective Adolescents who regularly use marijuana may be at heightened risk of developing subclinical and clinical psychotic symptoms. However, this association could be explained by reverse causation or other factors. To address these limitations, we examined whether adolescents who engage in regular marijuana use exhibit a systematic increase in subclinical psychotic symptoms that persists during periods of sustained abstinence. Method The sample comprised 1,009 boys who were recruited in 1st and 7th grades. Self-reported frequency of marijuana use, subclinical psychotic symptoms, and several time-varying confounds (e.g., other substance use, internalizing/externalizing problems) were collected annually from age 13 to 18. Fixed effects (within-individual change) models examined whether adolescents exhibited an increase in their subclinical psychotic symptoms as a function of their recent and/or cumulative history of regular marijuana use, and whether these effects were sustained following abstinence. Models controlled for all time-stable factors (default) and several time-varying covariates as potential confounds. Results For each year adolescents engaged in regular marijuana use, their expected level of subsequent subclinical psychotic symptoms rose by 21% (p <.05) and their expected odds of experiencing subsequent paranoia or hallucinations rose by 133% (p < .001) and 92% (p < .05), respectively. The effect of prior regular marijuana use on subsequent subclinical psychotic symptoms persisted even when adolescents stopped using marijuana for a year. Findings remained significant after controlling for all time-stable and several time-varying confounds, as well as possible reverse causation. Conclusions These results suggest that regular marijuana use may significantly increase the risk that an adolescent will experience persistent subclinical psychotic symptoms.

Cannabis Use, Polysubstance Use, and Psychosis Spectrum Symptoms in a Community-Based Sample of U.S. Youth

“…In contrast to recent findings in another US cohort [16], we found little evidence for associations between cannabis use by itself and PS symptoms. In adjusted analyses, neither frequent nor early cannabis use predicted increased odds of PS classification.…”

“…In other parts of the world the type of cannabis used (e.g., hash, skunk) and its cannabinoid concentrations may vary from the types used in the US [15], making generalizations to US samples challenging. To the best of our knowledge, associations between cannabis use and PS symptoms have only been examined in one other large cohort of non-help-seeking US adolescents [16,17]. In this sample of male adolescents, cannabis use did not predict the subsequent development of a psychotic disorder [17]; however, sustained cannabis use across adolescence predicted an increased risk of subclinical positive psychotic symptoms [16].…”

“…To the best of our knowledge, associations between cannabis use and PS symptoms have only been examined in one other large cohort of non-help-seeking US adolescents [16,17]. In this sample of male adolescents, cannabis use did not predict the subsequent development of a psychotic disorder [17]; however, sustained cannabis use across adolescence predicted an increased risk of subclinical positive psychotic symptoms [16]. Additional research with non-clinical samples of US youth is warranted to address the limitations of prior work and expand upon these initial findings.…”

“…As noted above, there has been minimal investigation into the links between cannabis use and PS symptoms in non-help-seeking US youth. The previous smaller scale US cohort study [16,17] only included male adolescents, did not examine the effects of polysubstance use on PS symptoms, did not examine subclinical negative/disorganized symptoms, and did not control for trauma exposure. We address these limitations in the present study.…”

Psychotic Symptoms in Attention-Deficit/Hyperactivity Disorder: An Analysis of the MTA Database

“…27-33 Specifically, it is the sustained, rather than sporadic, use of cannabis by adolescents that has been found to be associated with increased risk of subclinical psychotic symptoms, and especially paranoia. 29,30 The data from this study show that ADHD per se does not increase the risk for cannabis-associated psychotic symptoms.…”