Elsevier

Schizophrenia Research

Volume 170, Issue 1, January 2016, Pages 217-221
Schizophrenia Research

Cannabis use is associated with 3 years earlier onset of schizophrenia spectrum disorder in a naturalistic, multi-site sample (N = 1119)

https://doi.org/10.1016/j.schres.2015.11.027Get rights and content
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Abstract

Background

Patients with schizophrenia spectrum disorders and substance use may have an earlier onset of illness compared to those without substance use. Most previous studies have, however, too small samples to control for confounding variables and the effect of specific types of substances. The present study aimed to examine the relationship between substance use and age at onset, in addition to the influence of possible confounders and specific substances, in a large and heterogeneous multisite sample of patients with schizophrenia spectrum disorders.

Methods

The patients (N = 1119) were recruited from catchment areas in Oslo, Stavanger and Bergen, Norway, diagnosed according to DSM-IV and screened for substance use history. Linear regression analysis was used to examine the relationship between substance use and age at onset of illness.

Results

Patients with substance use (n = 627) had about 3 years earlier age at onset (23.0 years; SD 7.1) than the abstinent group (n = 492; 25.9 years; SD 9.7). Only cannabis use was statistically significantly related to earlier age at onset. Gender or family history of psychosis did not influence the results.

Conclusion

Cannabis use is associated with 3 years earlier onset of psychosis.

Keywords

Schizophrenia
Non-affective psychosis
Age at onset
Cannabis
Substance
Substance use

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