What is schizophrenia? 25 years of research into schizophrenia - the Age Beginning Course Study.

We studied a population-based sample of 232 first-onset cases of schizophrenia aged 12 to 59 years at first admission retrospectively back to illness onset and prospectively up to 11.2 years later. We compared them with psychiatrically healthy age- and sex-matched population controls and equally matched first-admission patients diagnosed with major depression. At schizophrenia onset women are several years older than men. The social factors tested did not explain the finding. Women's higher level of social development at onset is associated with a better medium-term functional and social outcome. Prodromal schizophrenia and depression are equal in length and diagnostically distinguishable only after the onset of positive symptoms. The sex difference in age at onset, invariable across cultures and ethnicities, is explained by a protective effect of oestrogen, which down-regulates D2 receptors. A higher genetic load antagonizes this effect. Long-term symptom-related illness course exhibits a plateau after three years, the positive symptom dimension after two years, the depressive and the negative dimensions do so after three to five years. The most prevalent symptom is depressive mood. Male first episodes are more frequent and more severe in the first half of life, female ones in the second half. Aetiological conclusions will be drawn.