Cannabis-Induced Psychosis-Like Experiences Are Associated with High Schizotypy

• Published in: Psychopathology Vol. 39; no. 4; pp. 175 - 178
• Main Authors: Barkus, E.J., Stirling, J., Hopkins, R.S., Lewis, S.
• Format: Journal Article
• Language: English
• Published: Basel, Switzerland Karger 01.01.2006; S. Karger AG
• Subjects: Adult; Adult and adolescent clinical studies; Biological and medical sciences; Cannabis; Female; Humans; Male; Marijuana Smoking - adverse effects; Marijuana Smoking - psychology; Medical sciences; Original Paper; Personality Assessment; Personality disorders; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Psychoses, Substance-Induced - etiology; Psychoses, Substance-Induced - psychology; Psychosis; Risk Factors; Schizotypal Personality Disorder - etiology; Schizotypal Personality Disorder - psychology; Surveys and Questionnaires; Schizotypy; Cannabis; Psychosis-like experiences; Psychosis; Schizotypal personality; Dicotyledones; Angiospermae; Cannabidaceae; Spermatophyta; Personality disorder
• ISSN: 0254-4962; 1423-033X
• DOI: 10.1159/000092678

Objective: Recent studies have suggested that cannabis use is a risk factor for developing schizophrenia. We tested the hypothesis that cannabis use increases the likelihood of psychosis-like experiences in non-clinical participants who scored highly on a measure of schizotypy. Method: The psychological effects of cannabis were assessed in 137 healthy individuals (76% female, mean age 22 years) using a newly developed questionnaire concerned with subjective experiences of the drug: the Cannabis Experiences Questionnaire. The questionnaire has three subscales: Pleasurable Experiences, Psychosis-Like Experiences and After-Effects. Respondents also completed the brief Schizotypal Personality Questionnaire. Results: Cannabis use was reported by 72% of the sample. Use per se was not significantly related to schizotypy. However, high scoring schizotypes were more likely to report both psychosis-like experiences and unpleasant after-effects associated with cannabis use. The pleasurable effects of cannabis use were not related to schizotypy score. Conclusion: High scoring schizotypes who use cannabis are more likely to experience psychosis-like phenomena at the time of use, and unpleasant after-effects. Our results are consistent with the hypothesis that cannabis use is a risk factor for full psychosis in this group.