Incidence and cumulative risk of treated schizophrenia

The present study uses data from the Prenatal Determinants of Schizophrenia (PDS) Study to derive age- and sex-specific estimates of incidence and cumu-lative risk for DSM-FV schizophrenia. Although not designed as an incidence study, the PDS Study uses both a well-defined population under continuous fol-lowup and DSM-IV diagnoses. The originating cohort was established in Alameda County, California, during 1959-1967 and yielded 12,094 cohort members fol-lowed from 1981 to 1997 during the principal ages at risk for schizophrenia. Survival analytic techniques showed that schizophrenia incidence rates per 10,000 person-years for men were 9.4 for ages 15-19; 5.6 for ages 20-24; 3 3 for ages 25-29; and 0.9 for ages 30-34. Schizophrenia incidence rates per 10,000 person-years for women were 1.6 for ages 15-19; 13 for ages 20-24; and 4.1 for ages 25-29. The cumulative risk for schizo-phrenia by age 38 was 0.93 percent for men and 035 percent for women. These estimates of incidence rates and risk were higher than those in traditional inci-dence studies but similar to recent Findings in other cohorts. Possible explanations for the apparently high rates of disorder include chance, design effects, and true variation in risk over time and place