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Cannabis and psychotic illness.

D C Mathers, A H Ghodse

The British Journal of Psychiatry November 1, 1992 DOI: 10.1192/bjp.161.5.648 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Observational cohort Peer reviewed
Population In-patients with psychotic symptoms and cannabis-positive urine analysis, compared with psychotic patients with drug-free urine analysis
Duration 6-month follow-up
Topics Cannabis
Key findings Cannabis-positive psychotic patients differed from drug-free patients on only five PSE items at one week, one item at one month, and none at six months, indicating no chronic cannabis-induced psychosis was found.

Abstract

In-patients with psychotic symptoms and cannabis-positive urine analysis were assessed by PSE within one week of admission and again at one and six months. Concurrently admitted psychotic patients with drug-free urine analysis were controls. At one week the two groups differed significantly on only five PSE items: changed perception, thought insertion, non-verbal auditory hallucinations, delusions of control, and delusions of grandiose ability. One item (delayed sleep) differed at one month, and none at six months. The symptom cluster at one week is consistent with acute cannabis intoxication. Subjects and controls were mostly single, poorly educated, unemployed people with histories of psychotic disorders, and given major tranquillisers on admission. Compared with controls, subjects were younger, less likely to have psychiatric histories, more often male, Afro-Caribbeans with a history of convictions and compulsory admissions. The commonest diagnosis was schizophrenia. Use of the label 'cannabis-induced psychosis' may obscure a diagnosis of paranoid schizophrenia. A short-lived psychotic episode does occur in clear consciousness after cannabis intoxication, but chronic cannabis-induced psychosis was not found.

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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