Follow-up studies of schizophrenia have reported divergent rates of outcomes. In addition to definition and measurement challenges, one reason for divergence may be due to sampling biases. Our aim was to report clinical and social outcomes of schizophrenia in the longitudinal, unselected, population-based Northern Finland 1966 Birth Cohort, and describe associated factors.

Subjects with DSM-III-R schizophrenia (N=109) were followed prospectively from mid-pregnancy up to age 35 years. Used outcome measures were positive and negative symptoms, global clinical impression, use of antipsychotics, psychiatric hospitalisations, social and occupational functioning. Several definitions of good and poor outcomes were explored, and predictors of outcomes were analysed.

In a subsample of 59 cases with complete information of outcomes, good clinical outcome varied from 10% to 59%, and good social outcome 15-46%, depending on definition of outcomes. Poor clinical outcome varied 41-77% and poor social 37-54%. Two subjects recovered fully using the most stringent definition of outcome. Lack of friends in childhood, father's high social class, lower school performance and earlier age of illness onset predicted poor outcomes. When the whole sample was considered, early infant development around the age of 1 year was associated with worse course of illness.

Outcomes were heterogeneous and relatively poor in this sample of relatively young schizophrenia subjects. The results were influenced by the definitions and measurements of outcomes. Persons having a sub-optimal developmental trajectory with poor social contacts, poor school performance, and early age of illness onset seem to have the worst outcome.