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Polydrug use, cannabis, and psychosis‐like symptoms

Nicholas T. van Dam, Mitch Earleywine, Greg DiGiacomo

Human Psychopharmacology: Clinical and Experimental August 1, 2008 DOI: 10.1002/hup.950 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Observational cohort Peer reviewed
Sample size 471
Population People with different exposure to cannabis, including weekly, monthly, former, and non-users
Measures Schizotypal Personality Questionnaire (SPQ)
Topics Cannabis
Key findings Cannabis use was associated with higher SPQ scores, but this association was accounted for by other drug use, particularly psychomotor stimulants and ecstasy. Users of only cannabis and legal drugs did not differ from legal-drug-only users, and both scored lower than polydrug users.

Abstract

AbstractObjectiveTo examine psychosis‐like symptoms in users of legal and illicit drugs.MethodsSchizotypal Personality Questionnaire (SPQ) scores were compared in groups of people with different exposure to cannabis, with the use of other drugs serving as a covariate. Supplemental analyses compared users of legal and illicit drugs with cannabis use as a covariate.ResultsWeekly (n = 111) and monthly (n = 136) cannabis users had higher scores on the SPQ than former (n = 143) and non‐users (n = 81). The use of other drugs accounted for the links between cannabis and schizotypy. Lifetime use of psychomotor stimulant drugs plus ecstasy accounted for associations between cannabis and scores on the SPQ and its different subscales. Dividing groups by type of drug use revealed that those who used only cannabis and legal drugs (CLDs) (n = 126) were no different from those who used only legal drugs (LDs) (n = 74) but both groups scored significantly lower on the SPQ than polydrug users (n = 247). When controlling for marijuana use in the last month, the significant difference across drug use groups remained.ConclusionsThe results suggest that research on marijuana and schizotypy requires careful assessment of the use of other drugs, especially psychomotor stimulants and ecstasy. Copyright © 2008 John Wiley & Sons, Ltd.

Comparable studies

Other observational and cohort studies on cannabis, most cited first.

Study Year Design Participants
High-potency cannabis and the risk of psychosis People with first episode of psychosis and healthy controls from the local population 2009 Case-control study n = 454
Ayahuasca-Assisted Therapy for Addiction: Results from a Preliminary Observational Study in Canada Rural aboriginal population 2013 Observational study
Impaired cognitive performance in drug free users of recreational ecstasy (MDMA) Otherwise healthy young people 2000 Observational
Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study Individuals from the general population in Germany aged 14-24 at baseline 2011 Observational cohort n = 1,923
Cannabis-induced psychosis and subsequent schizophrenia-spectrum disorders: follow-up study of 535 incident cases Patients treated for cannabis-induced psychotic symptoms in Denmark between 1994 and... 2005 Observational cohort n = 535

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