Measuring psychotherapeutic change with the symptom checklist SCL 90 R

Despite a long tradition of discussions on the evaluation of psychotherapy, there is still a lack of agreement for measuring change after psychological treatment. In this paper we describe the concept of statistical and clinical significance of change. We use the Symptom Checklist 90 R as a commonly administered instrument to propose conventions and cutoff points for psychological symptoms and their change after therapy.

A German norm population and several psychotherapy samples have been aggregated to calculate cutoffs and confidence intervals (reliable change indices) for statistically and clinically significant changes after psychotherapy.

The cutoff point between a 'functional' and a 'dysfunctional' population was calculated as C = 0.57 (Global Severity Index, GSI). Patients above this score need a change of at least RCI = 0.43 (GSI difference) for a statististically significant change. Below this score the RCI = 0.16. The use of multiple clinical groups (e.g. inpatients and outpatients) for a more realistic determination of a 'stepwise' clinically significant change, as proposed by Tingey et al. in the USA, is not possible in the German samples collected so far. Initial SCL 90-R scores in these groups do not show enough differences to call a move from one group to the other a clinically significant change.

In the German samples investigated the move from a 'functional' to a 'dysfunctional' population and vice versa has to be taken as the criterion for a clinically significant change up to now.