Changes in the diagnosed incidence of early onset schizophrenia over four decades

Abstract

To explore changes in the diagnosed incidence of early onset schizophrenia (EOS) from 1971 to 2010. Examination of incidence rates of schizophrenia in patients under 18 years of age, using a nationwide, population-based, mental health register. The age-standardized incidence rate (IR) of EOS in the period 1971-2010 was 3.17 (95% CI: 3.16, 3.18) per 100 000 person years in the age group 0-18 years, and 9.10 (95% CI: 9.00, 9.21) in the age group 12-18 years. In the period 1971-1993, the age-standardized IR of EOS was 1.80 (95% CI: 1.79, 1.82) per 100 000 person years in the age group 0-18 years, and 5.02 (95% CI: 4.92, 5.11) in the age group 12-18 years. In the period 1994-2010, the age-standardized IR of EOS was 5.15 (95% CI: 5.10, 5.20) per 100 000 person years in the age group 0-18 years, and 15.73 (95% CI: 15.22, 16.22) in the age group 12-18 years. The IR was higher for males than females in the periods 1971-1993 and 1971-2010, but in the period 1994-2010 the IR was higher for females than males. In recent years, the diagnosed incidence of EOS has increased and the usual male excess has disappeared. The changes in IR could be a result of changes in the diagnostic system, increased awareness of early psychosis or a reflection of actual underlying incidence of the disorder.