The effects of tobacco smoking on age of onset of psychosis and psychotic symptoms in a first-episode psychosis population

Abstract

BACKGROUND AND AIMS: Research suggests that tobacco smokers may develop psychosis at an earlier age than non-smokers, with effects on psychotic symptoms. We aimed to test the difference in age of onset of psychosis between smokers and non-smokers.

DESIGN: Self-report data were collected from smokers and non-smokers in a population of first-episode psychosis patients.

SETTING: Out-patient first-episode psychosis programme in Santander (Cantabria), Spain.

PARTICIPANTS: Three hundred and ninety-seven patients (226 male, 171 female) who agreed to take part between 2001 and 2011.

MEASUREMENTS: Age of onset of psychosis, age of smoking initiation, demographics, family history of psychosis and cannabis use were collected by self-report.

FINDINGS: Kaplan-Meier analysis showed that smokers had a significantly lower mean age of psychosis onset [smokers = 27.4 (± 8.1) years, non-smokers = 30.5 (± 9.9) years] than non-smokers (?2(1) = 11.72, P = 0.001). The Cox proportional hazard model showed no significant difference in the age of psychosis onset between smokers and non-smokers adjusted for covariates [hazard ratio (HR) = 1.034, 95% confidence interval (CI) = 0.828-1.291]. Age of psychosis onset was predicted significantly by cannabis use (HR = 2.073, 95% CI = 1.633-2.633) and gender (HR = 1.706, 95% CI = 1.363-2.135).

CONCLUSIONS: Smokers do not appear to have a significantly earlier age of psychosis onset than non-smokers after taking into account cannabis use and gender.