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

OBJECTIVE: To explore changes in the diagnosed incidence of early onset schizophrenia (EOS) from 1971 to 2010.

METHOD: Examination of incidence rates of schizophrenia in patients under 18 years of age, using a nationwide, population-based, mental health register.

RESULTS: 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.

CONCLUSION: 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.