title: The effects of tobacco smoking on age of onset of psychosis and psychotic symptoms in a first-episode psychosis population.
abstract: 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.
  
  
  
  Self-report data were collected from smokers and non-smokers in a population of first-episode psychosis patients.
  
  
  
  Out-patient first-episode psychosis programme in Santander (Cantabria), Spain.
  
  
  
  Three hundred and ninety-seven patients (226 male, 171 female) who agreed to take part between 2001 and 2011.
  
  
  
  Age of onset of psychosis, age of smoking initiation, demographics, family history of psychosis and cannabis use were collected by self-report.
  
  
  
  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 (χ2(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).
  
  
  
  Smokers do not appear to have a significantly earlier age of psychosis onset than non-smokers after taking into account cannabis use and gender.
authors.affiliation: Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
authors.forename: Lauren M
authors.initials: LM
authors.lastname: Hickling
authors.affiliation: IDIVAL, Marqués de Valdecilla University Hospital, Santander, Spain.|Department of Psychiatry, School of Medicine, University of Cantabria, Santander, Spain.|CIBERSAM, Centro Investigación Biomédica en Red Salud Mental, Santander, Spain.
authors.forename: Victor
authors.initials: V
authors.lastname: Ortiz-García de la Foz
authors.affiliation: IDIVAL, Marqués de Valdecilla University Hospital, Santander, Spain.|Department of Psychiatry, School of Medicine, University of Cantabria, Santander, Spain.|CIBERSAM, Centro Investigación Biomédica en Red Salud Mental, Santander, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Ayesa-Arriola
authors.affiliation: IDIVAL, Marqués de Valdecilla University Hospital, Santander, Spain.|Department of Psychiatry, School of Medicine, University of Cantabria, Santander, Spain.|CIBERSAM, Centro Investigación Biomédica en Red Salud Mental, Santander, Spain.
authors.forename: Benedicto
authors.initials: B
authors.lastname: Crespo-Facorro
authors.affiliation: Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
authors.forename: Philip
authors.initials: P
authors.lastname: McGuire
authors.affiliation: Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.|CIBERSAM, Centro Investigación Biomédica en Red Salud Mental, Santander, Spain.
authors.forename: Rocio
authors.initials: R
authors.lastname: Perez-Iglesias
mesh_terms: D000328:Adult; D017668:Age of Onset; D015897:Comorbidity; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D010045:Outpatients / Q000523:psychology; D016016:Proportional Hazards Models; D011618:Psychotic Disorders / Q000453:epidemiology* / Q000523:psychology; D057566:Self Report; D000074285:Smokers / Q000523:psychology / Q000706:statistics & numerical data*; D012907:Smoking / Q000453:epidemiology*; D013030:Spain
keywords: Age of onset; first-episode psychosis; psychopathology; psychosis; smoking; tobacco