Background: It is important to know the stability of standard outcome measures prior to therapy over differing periods of time that map onto the realities of waiting times in routine service settings.
Method: We studied 1,684 clients who completed one or both the targeted measures Clinical Outcomes in Routine Evaluation-Outcome Measures (CORE-OM) and Beck Depression Inventory-I (BDI-I) two times, at intervals of up to 12 months, prior to beginning psychotherapy. We also selected an additional 1,623 clients who completed the CORE-OM (N=1,623), BDI-I (N=980) or both at referral, but had no records of further contact with the service.
Results: There was little change in the mean CORE-OM or BDI-I scores between referral and clinical assessment. The test-retest correlations showed substantial stability on both measures, declining only moderately at the longer intervals studied.
Conclusion: The high test-retest correlations for periods of up to 6 months suggest that psychological disturbance was both reliably measured by the CORE-OM and the BDI-I, and reasonably stable among clients waiting to be assessed. Implications for routine practice are discussed.