OBJECTIVE: Primary care is the de facto mental health system in the United States where physicians treat large numbers of depressed older adults with antidepressant medication. This study aimed to examine whether antidepressant dosage adequacy and patient adherence are associated with depression response among middle-aged and older adults prescribed with antidepressants by their primary care provider.

DESIGN: A secondary analysis was conducted on a sample drawn from a randomized controlled trial comparing Treatment as Usual to Treatment Initiation Program, an adherence intervention. Treatment Initiation Program improved adherence but not depression compared to Treatment as Usual (Sirey et al., 2017). For this analysis, we examined dosing adequacy and adherence at 6 and 12 weeks as predictors of depression response in both groups at 12 and 24 weeks.

SETTING: Primary care practices.

PARTICIPANTS: One hundred eighty-seven older adults with depression prescribed an antidepressant for depression by their primary care provider.

MEASUREMENTS: Depression response was defined as 50% reduction on the Hamilton Rating Scale for Depression. Adherence was defined as taking 80% of doses at follow-up interviews (6 and 12 weeks). Patient-reported dosage and duration of antidepressant therapy was collected using the Composite Antidepressant Score (adequacy score of >3) at follow-up.

RESULTS: Greater adherence, but not receipt of adequate dosage, was associated with higher likelihood of treatment response at both 12 (Odds ratio (OR) = 2.63; 95% Confidence Interval (CI), 1.19-5.84) and 24 weeks (OR = 3.09; 95% CI, 1.46-6.55).

CONCLUSION: As physicians prescribe antidepressants to the diverse group of adults seen in primary care, special attention to patients' views and approach to adherence may improve depression outcomes.