Changes in patients' beliefs about their antidepressant during the acute phase of depression treatment

To test hypotheses regarding medication beliefs in relation to adherence, side effects, and response during the acute phase of an antidepressant treatment episode.

Participants were 163 patients with unipolar major depression participating in the acute phase of a multi-stage trial of medication and psychotherapy. Before starting citalopram, patients underwent measures of treatment beliefs and depression. They continued taking citalopram until either responding, discontinuing due to side effects, or failing to respond within 14 weeks. Assessments of adherence, side effects and depression were made at weeks 2, 4, 6, 9, 12 and 14 (as applicable) and at trial exit. Beliefs were reevaluated at exit.

Perceived need for medication increased between baseline and exit (P=.01) while perceived medication harmfulness dropped between baseline and exit (P<.0001). Adherence was related to baseline perceived need (P=.022), and side effects were related to baseline perceived harmfulness (P=.002). Change in depressive symptoms was significantly related to both baseline perceived need (P=.039) and mean adherence (P=.036) but not baseline perceived harmfulness (P=.184) or side effects (P=.102). At exit, perceived need was unrelated to change in depression severity (P=.565), while perceived harmfulness was related to prior side effects (P<.0001).

Patients' medication perceptions become more pro-adherence as treatment proceeds. Their perceptions of antidepressant necessity predict their subsequent medication adherence and response, while their perceptions about medication harmfulness show strong prospective associations with actual side effects. Clinicians ought to adjust their prescribing decisions accordingly. Interventions that target beliefs ought to capitalize upon the apparently bidirectional association between harm perceptions and actual side effects.