Duration of psychotherapy and outcome in standard practice settings

Robert A. Coombs, (2000)

This study showed that a "dose-effect" strategy can be used effectively to investigate the relationship between duration and outcome. The relationship was investigated for adult outpatients in both public mental health (N = 63) and private practice settings (N = 10). Clients completed a Problem Rating scale and the Brief Symptom Inventory (BSI) at intake (Time 1), about 3 months or 8 sessions later (Time 2), and between 5 to 7 months or 10 to 12 sessions after intake (Time 3). The interval between Time 1 and Time 2 was defined as Phase 1 while the interval between Time 2 and Time 3 was defined as Phase 2. Therapists' Problem Ratings of client improvement were obtained at Time 1 and Time 3 for the public mental health settings and at all three time points for the private practice settings. A sequence of both parametric and nonparametric analyses were used to assess outcome. First, the outcome of clients who continued in treatment past Time 2 assessed whether continuance past 3 months was associated with an increased benefit in outcome--an assessment of the dose-effect in outpatient psychotherapy. Secondly, the outcomes for clients who terminated before Time 2 were compared with clients who stayed in treatment past Time 2. This comparison assessed whether outcome was the same for briefer vs. longer term psychotherapy. In addition, Jacobson and Truax's (1991) method of measuring clinical significance was used for the same analyses. The results of these different analyses showed that most clinical improvement occurred during Phase 1, about the eighth session, and then levelled off. However, different measures appeared to improve at different rates. There was a trend for objective symptoms to improve before clients rated themselves improved. A few clients experienced a "failure zone" or dip in improvement during treatment while a few others deteriorated during treatment. These results were discussed and recommendations for further studies were suggested.