[The impact of the study design and the sampling procedure on the assessment of mental health services].

In this paper the impact of the study design and the sampling procedure on the assessment of the costs of schizophrenia treatment will be analyzed. The study sample consists of 307 patients with the diagnosis of schizophrenia (ICD 10F20) with the age between 18 and 65 years. Study participants were recruited consecutively in inpatient and outpatient treatment settings and in accommodation facilities according to the proportions of patients treated in these settings in Leipzig which have been assessed before. Treatment costs have been assessed by means of the German version of the Client Sociodemographic and Service Receipt Inventory at five follow-ups at six-months intervals. For the whole study period significant differences of the mean service costs due to the recruitment setting have been found. The mean yearly costs amounted to 44.669 DM for participants recruited in sheltered accommodation, 27.975 DM for participants in inpatient treatment and 5691 DM for patients in outpatient facilities. A random-effect regression model confirmed significant effects of the recruitment setting over all five follow-ups. Additionally, the variance of costs over time indicates that cost assessment by means of cross sectional data involves the danger of errors due to random dispersion.