- Objectives: To evaluate patient and physician characteristics associated with the purchase of antidepressant medication for at least 6 months. Clalit Health Services is the largest managed care health fund in Israel, a country that uses a universal healthcare system. We randomly sampled 30,000 primary care patients over the age of 22 years. Our analytic sample consisted of those 949 patients who did not purchase antidepressant medication during the last quarter of 2005 and purchased antidepressant medication at least once in 2006. We used multilevel analysis, with whether or not medication was purchased for at least 6 months as an indicator of adherence. Patient and physician characteristics were evaluated as potential predictors. Only 23% of the sample was classified as adherent. Physician characteristics explained only a small portion of the variance in adherence and, as a result, were not included in multivariate analysis. Patients who did not have a somatic diagnosis, had a depression diagnosis, and were of higher socioeconomic status were more likely to be classified as adherent. Patients who purchased tricyclic antidepressants were less likely to be classified as adherent. The findings suggest that in a managed care setting, there is high uniformity among physicians. Although physician characteristics explain little of the variability associated with adherence, certain patient characteristics as determined by their physicians (eg, antidepressant drug class, psychiatric diagnosis) do play a role in adherence.