Identifying predictors of a favourable outcome for outpatients with a persistent depressive disorder treated with Cognitive Behavioural Analysis System of Psychotherapy: A prospective cohort study

Objectives: Cognitive Behavioural Analysis System of Psychotherapy (CBASP) is the first therapy specifically developed for persistent depressive disorder (PDD). This study aimed to identify predictors of favourable treatment outcome after group CBASP and assess change in depression severity over 24 weeks. Design: A prospective cohort study was conducted in patients with PDD treated with group-CBASP. Methods: Outcomes were depression severity measured by the Inventory of Depression Severity-self-report (IDS-SR) after 6 and 12 months. Potential predictors investigated were baseline depression severity, prior antidepressant use, age, family status, income source, age of onset and childhood trauma. Multivariate logistic regression was performed to assess their effects with a >= 25% IDS-SR score decrease as the dependent variable. Results: The IDS-SR score (range 0-84) significantly decreased from 37.78 at start to 33.45 at 6 months, an improvement which was maintained at 12 months. Having paid work and no axis I comorbidity significantly predicted favourable response. In the groups without a favourable outcome predictor a substantial percentage still showed at least partial response (16.7% and 19.2%). Conclusions: Source of income and axis I comorbidity were predictors of response to group-CBASP. Within the group without favourable outcome predictors, a subgroup showed at least partial response. These results suggest that group-CBASP has promise for patients who do not respond to standard treatments. Future studies should include outcome measures that take into account comorbidity and other clinically relevant changes, such as social functioning.