title: Admixture analysis of age at onset in schizophrenia: evidence of three subgroups in a first-episode sample.
abstract: OBJECTIVE
  The objective was to assess the presence of different subgroups, via age-at-onset (AAO) analysis, in a schizophrenia population consecutively recruited through an Early Psychosis Service in London, Canada.
  
  
  METHODS
  Admixture analysis was applied in order to identify a model of separate normal distribution of AAO characterized by different means, variances and population proportions to allow for evaluation of different subgroups in a sample of 187 unrelated patients with a Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, diagnosis of schizophrenia.
  
  
  RESULTS
  The best-fitting model suggested three subgroups with means and standard deviations of 16.8 ± 1.9, 22.3 ± 2.1 and 32.7 ± 5.9 years comprising 41%, 30% and 29% of the schizophrenia sample, respectively. These three subgroups were categorized as early, intermediate and late onset with cutoffs determined by admixture analysis to be 19 and 26 years of age, respectively. In our investigation, the definition of early-onset schizophrenia is the main outcome. We considered the clinical variables mainly related to the heritability and neurobiology of schizophrenia. Single status was strongly associated with early onset (P<.001). The male gender (P=.023), as well as a history of drug abuse (P=.004), was significantly associated with early onset. Interestingly, lower academic achievement was also associated with early-onset schizophrenia (P<.001).
  
  
  CONCLUSIONS
  Overall, our study showed that a typical early-onset schizophrenia patient is more likely to be a single male, with a history of drug abuse and birth complications, and lower academic achievement as compared to the late-onset subgroup.
authors.affiliation: Department of Family and Community Medicine, University of Toronto, Toronto, Canada.
authors.forename: Jerome J
authors.initials: JJ
authors.lastname: Liu
authors.forename: Ross M G
authors.initials: RM
authors.lastname: Norman
authors.forename: Raul
authors.initials: R
authors.lastname: Manchanda
authors.forename: Vincenzo
authors.initials: V
authors.lastname: De Luca
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D017668:Age of Onset; D002170:Canada; D015331:Cohort Studies; D004522:Educational Status; D005260:Female; D006801:Humans; D008297:Male; D017533:Marital Status / Q000706:statistics & numerical data; D015233:Models, Statistical; D012559:Schizophrenia / Q000453:epidemiology*; D017678:Sex Distribution; D019966:Substance-Related Disorders / Q000453:epidemiology; D055815:Young Adult
keywords: Admixture analysis; Age at onset; Recall bias; Schizophrenia