Importance: Nonadherence to antidepressant medication is common and leads to poor outcomes. Early nonadherence is especially problematic.

Objective: To test the effectiveness of a psychosocial intervention to improve early adherence among older patients whose primary care physician newly initiated an antidepressant for depression.

Design, Setting, and Participants: The Treatment Initiation and Participation Program (TIP) was offered in a 2-site randomized clinical effectiveness study between January 2011 and December 2014 at primary care practices in New York, New York, and Ann Arbor, Michigan. Analyses began in February 2016. All participants were middle-aged and older adults (aged ≥55 years) who received newly initiated depression treatment by their primary care physician and recruited within 10 days of their prescription. Analyses were intention-to-treat.

Interventions: Participants were randomly assigned to the intervention (TIP) or treatment as usual. Participants in the TIP group identified and addressed barriers to adherence, including stigma, misconceptions, and fears about treatment, before developing a personalized adherence strategy. The Treatment Initiation and Participation Program was delivered in three 30-minute contacts scheduled during a 6-week period just after the antidepressant was prescribed.

Main Outcomes and Measures: The primary outcome was self-reported adherence on the Brief Medication Questionnaire, with adequate early adherence defined as taking 80% or more of the prescribed doses at 6 and 12 weeks. The secondary outcome was depression severity.

Results: In total, 231 middle-aged and older adults (167 women [72.3%] and 64 men [27.7%]) without significant cognitive impairment were randomly assigned to the TIP intervention (n = 115) or treatment as usual (n = 116). Participants had a mean (SD) age of 67.3 (8.4) years. Participants in the TIP group were 5 times more likely to be adherent at 6 weeks (odds ratio, 5.54; 95% CI, 2.57 to 11.96; χ21 = 19.05; P < .001) and 3 times more likely to be adherent at both 6 and 12 weeks (odds ratio, 3.27; 95% CI, 1.73 to 6.17; χ21 = 13.34; P < .001). Participants in the TIP group showed a significant earlier reduction (24.9%) in depressive symptoms (95% CI, 13.9 to 35.9; t337 = 4.46; adjusted P < .001). In both groups, participants who were 80% adherent at weeks 6 and 12 had a 15% greater improvement in depressive symptoms from baseline over the course of treatment (95% CI, -0.2 to -30; t369 = 1.93; P = .051).

Conclusions and Relevance: The Treatment Initiation and Participation Program is an effective intervention to improve early adherence to pharmacotherapy. Improved adherence can promote improvement in depression.

Trial Registration: clinicaltrials.gov Identifier: NCT01301859.