BACKGROUND: Patient beliefs in the effectiveness of treatment may havean important influence on treatment outcome. MATERIAL/METHODS: Associations between patient beliefs inthe credibility of treatment and outcome were explored in a randomised controlled trial of major depressionin primary care (n=155). The four treatments were antidepressant medication given by research generalpractitioner, problem solving treatment given by research general practitioner or research practice nurseover 12 weeks or a combination of problem solving treatment and antidepressant medication. Patients'belief in the credibility of treatment was assessed using a brief Credibility Scale, that was completedfollowing randomisation and after treatment. Depression outcome was measured at 6, 12 and 52 weeks usingthe Hamilton Rating Scale for depression, and the Beck depression inventory. RESULTS: Pre-treatment,medication treatment was associated with a higher certainty of recovery than was problem-solving treatmentfrom the nurse (p=0.018). Post-treatment, medication and combination treatment were seen as more logicalthan problem-solving treatment from the nurse (p<0.03). Post-treatment medication had higher certainty of recovery and was more highly recommended to a friend. Linear regression demonstrated that the depression outcome measures were not associated with either pre- or post-treatment credibility.
Conclusions: Patients found all four treatments highly credible following their initial explanation. There was a significant difference both pre- and post-treatment in favour of patients finding treatment involving medication more credible than problem-solving from a nurse. Pre- and post-treatment scores of credibility were not associated with outcome

Keywords: Adolescent, Antidepressive Agents, Second-Generation, Depression, fluvoxamine, paroxetine, Psychotherapeutic Processes, Time Factors