Social disability in schizophrenia: the controlled prospective Burghölzli study. I. Case-finding, research design, and characteristics of samples.

The Psychiatric University Hospital Zürich (Burghölzli') is taking part in the 'WHO Collaborative Study on the Assessment and Reduction of Psychiatric Disability'. This multicenter project aims to assess the development of social disability for schizophrenic psychoses of relatively recent onset. This paper provides a brief review of underlying concepts, the prospective procedure, and the screening criteria applying to all centers. The research team at 'Burghölzli' has greatly extended the general design. Apart from the "obligatory" assessment of 69 first admitted schizophrenics (initial assessment on first hospitalization or outpatient treatment and follow-ups after 1, 2, and 5 years) we have also interviewed a control sample of 60 healthy persons (including a 2-year follow-up) and an 'extreme' sample of 46 chronic schizophrenic outpatients legally entitled to disability pension. Moreover, we have used several supplementary assessment instruments. This paper is to discuss the purpose of our extended research design. All cohorts are described with respect to screening criteria, sampling procedure, and some basic characteristics; furthermore, a review is given of the additional assessment instruments. It is intended to provide basic information for subsequent papers dealing with results from the study.