[Institutionalisation-index--a simple method to estimate direct treatment costs for institutionalised forms of community mental health care].

Aim: Investigations of treatment costs are of increasing importance in community mental health care. Yet, they are often difficult and expensive to conduct. This study explores whether and, if so, to what extent direct treatment costs as paid by insurance companies and social welfare in the German health care system can be estimated through a simple Institutionalisation-Index.

Method: Based on the literature and clinical judgment, a simple Institutionalisation-Index was formed reflecting the degree of institutional protection in supported housing, long-term day care, partial hospitalisation and full hospitalisation programmes. As part of a comprehensive evaluation of a model institution for community mental health care in Berlin, actually paid treatment costs and Institutionalisation-Index (II) were identified for 1194 patients over a total period of 23 years and compared with each other.

Results: The Pearson correlation coefficient between II and paid costs was 0.97 (p < 0,001). In calculations for subgroups and different periods of time, II and costs were almost identical, too.

Conclusions: The Institutionalisation-Index provides a sufficiently precise estimate of direct costs as paid by insurance companies and social welfare for different forms of care in community based institutions and hospitals. The II can be adjusted to incorporate further forms of community based care. In systems with similar funding arrangements, the simple method to establish a Institutionalisation-Index should facilitate cost analyses in community mental health care.