title: A comparison of the cumulative incidence and early risk factors for psychotic disorder in young adults in the Northern Finland Birth Cohorts 1966 and 1986.
abstract: Few studies have compared time trends for the incidence of psychosis. To date, the results have been inconsistent, showing a decline, an increase or no significant change. As far as we know, no studies explored changes in prevalence of early risk factors. The aim of this study was to investigate differences in early risk factors and cumulative incidences of psychosis by type of psychosis in two comparable birth cohorts.
  
  
  
  The Northern Finland Birth cohorts (NFBCs) 1966 (N = 12 058) and 1986 (N = 9432) are prospective general population-based cohorts with the children followed since mother's mid-pregnancy. The data for psychoses, i.e. schizophrenia (narrow, spectrum), bipolar disorder with psychotic features, major depressive episode with psychotic features, brief psychosis and other psychoses (ICD 8-10) were collected from nationwide registers including both inpatients and outpatients. The data on early risk factors including sex and place of birth of the offspring, parental age and psychosis, maternal education at birth were prospectively collected from the population registers. The follow-up reached until the age of 27 years.
  
  
  
  An increase in the cumulative incidence of all psychoses was seen (1.01% in NFBC 1966 v. 1.90% in NFBC 1986; p < 0.001), which was due to an increase in diagnosed affective and other psychoses. Earlier onset of cases and relatively more psychoses in women were observed in the NFBC 1986. Changes in prevalence of potential early risk factors were identified, but only parental psychosis was a significant predictor in both cohorts (hazard ratios ≥3.0; 95% CI 1.86-4.88). The difference in psychosis incidence was not dependent on changes in prevalence of studied early risk factors.
  
  
  
  Surprisingly, increase in the cumulative incidence of psychosis and also changes in the types of psychoses were found between two birth cohorts 20 years apart. The observed differences could be due to real changes in incidence or they can be attributable to changes in diagnostic practices, or to early psychosis detection and treatment.
authors.affiliation: Center for Life Course Health Research,University of Oulu,Oulu,Finland.
authors.forename: S
authors.initials: S
authors.lastname: Filatova
authors.affiliation: Center for Life Course Health Research,University of Oulu,Oulu,Finland.
authors.forename: R
authors.initials: R
authors.lastname: Marttila
authors.affiliation: Institute of Clinical Medicine (Psychiatry), University of Eastern Finland,Kuopio,Finland.
authors.forename: H
authors.initials: H
authors.lastname: Koivumaa-Honkanen
authors.affiliation: Center for Life Course Health Research,University of Oulu,Oulu,Finland.
authors.forename: T
authors.initials: T
authors.lastname: Nordström
authors.affiliation: Medical Research Center Oulu,Oulu University Hospital and University of Oulu,Oulu,Finland.
authors.forename: J
authors.initials: J
authors.lastname: Veijola
authors.affiliation: Medical Research Center Oulu,Oulu University Hospital and University of Oulu,Oulu,Finland.
authors.forename: P
authors.initials: P
authors.lastname: Mäki
authors.affiliation: Department of Psychiatry,University of Cambridge,Cambridge,UK.
authors.forename: G M
authors.initials: GM
authors.lastname: Khandaker
authors.affiliation: Department of Psychiatry,Center of Clinical Neuroscience,University of Oulu,Oulu,Finland.
authors.forename: M
authors.initials: M
authors.lastname: Isohanni
authors.affiliation: Center for Life Course Health Research,University of Oulu,Oulu,Finland.
authors.forename: E
authors.initials: E
authors.lastname: Jääskeläinen
authors.affiliation: Medical Research Center Oulu,Oulu University Hospital and University of Oulu,Oulu,Finland.
authors.forename: K
authors.initials: K
authors.lastname: Moilanen
authors.affiliation: Center for Life Course Health Research,University of Oulu,Oulu,Finland.
authors.forename: J
authors.initials: J
authors.lastname: Miettunen
mesh_terms: D000328:Adult; D016241:Child of Impaired Parents / Q000523:psychology* / Q000706:statistics & numerical data; D015331:Cohort Studies; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D009035:Mothers / Q000523:psychology* / Q000706:statistics & numerical data; D011247:Pregnancy; D011446:Prospective Studies; D011618:Psychotic Disorders / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology; D012042:Registries; D012559:Schizophrenia / Q000175:diagnosis / Q000453:epidemiology*; D012565:Schizophrenic Psychology; D055815:Young Adult
keywords: Cumulative incidence; early risk factors; psychosis; schizophrenia