Objective: To examine outcomes of primary care patients receiving low levels of antidepressant treatment.
Design: Cohort study comparing patients receiving anti-depressant treatment within and below the recommended dosing range.
Setting: Primary care clinics of a staff-model health maintenance organization.
Patients: Primary care patients initiating antidepressant treatment for depression.
Measurements and main results: Of 88 patients beginning antidepressant treatment, 49 (56%) used "adequate" doses for 30 days or more. Likelihood of "adequate" pharmacotherapy was not related to patient age, gender, medical comorbidity, or baseline depression severity. All the patients showed substantial clinical improvement after four months. Compared with those using "adequate" pharmacotherapy, the patients receiving low-intensity treatment had lower likelihood of clinical response (64% vs 84%; chi-square = 4.44; df = 1; p = 0.035). At four months, however, those receiving low-intensity and those receiving higher-intensity treatment did not differ significantly in either the score on the 20-item Symptom Checklist depression scale (18.91 and 15.72, respectively; F = 1.45; df = 1.86; p = 0.23) or the proportion with persistence of major depression (10% and 4%, respectively; chi-square = 1.30; df = 1; p = 0.25). A replication sample of 157 patients (assessed only at baseline and four months) yielded similar results.
Conclusions: While the patients receiving recommended levels of pharmacotherapy showed somewhat higher improvement rates, many of the patients receiving "inadequate" treatment experienced good short-term outcomes. Efforts to increase the intensity of depression treatment in primary care should focus on the subgroup of patients who fail to respond to initial treatment.