Objectives: The aims of this study were to use symptom intensity measures collected at each session (1) to describe the outcomes of clients who received cognitive therapy (CT) for depression in a clinically representative sample, and (2) to compare the outcomes of clients who completed the agreed number of sessions with those who did not.
Design and method: Clients (N = 58) contracted to attend between 12 and 20 sessions of CT completed the Beck Depression Inventory (BDI) immediately prior to each therapy session. The BDI and other measures were collected at intake and, for those who completed therapy, at a post-therapy assessment.
Results: Completers' BDI scores improved significantly from intake to post-treatment and significantly more from intake to their final session than did those of non-completers. However, when non-completers' final session scores were matched with scores of randomly selected completers at the corresponding session, the difference in improvement was not significant. A significantly higher proportion of clients who completed the agreed number of sessions achieved reliable and clinically significant change (71.4%, 25/35), compared with just 13% (3/23) of clients who did not.
Conclusions: (1) CT for depression can be effective in a clinically representative population. (2) Attrition from clinical trials may bias estimates of treatment effectiveness.