Does recognition of depression in primary care affect outcome? The PREDICT-NL study

Background. Detection rates of depression in primary care are <50%. Studies showed similar outcome after 12 months for recognized and unrecognized depression. Outcome beyond 12 months is less well studied. Objective. We investigated recognition of depression in primary care and its relation to outcome after 6, 12 and 39 months. Methods. Data were used from a prospective cohort study of 1293 consecutive general practice attendees (PREDICT-NL), who were followed up after 6 (n = 1236), 12 (n = 1179) and 39 (n = 752) months. We measured the presence and severity of major depressive disorder (MDD) according to DSM-IV criteria and Patient Health Questionnaire 9 (PHQ-9) and mental function with Short Form 12 (SF-12). Recognition of depression was assessed using international classification of primary care codes (P03 and P76) and Anatomical Therapeutic Chemical (N06A) codes from the GP records (6 months before/after baseline). Results. At baseline, 170 (13%) of the participants had MDD, of whom 36% were recognized by their GP. The relative risk of being depressed after 39 months was 1.35 [95% confidence interval (CI) 0.7-2.7] for participants with recognized depression compared to unrecognized depression. At baseline, participants with recognized depression had more depressive symptoms (mean difference PHQ-9 2.7, 95% CI 1.6-3.9) and worse mental function (mean difference mental component summary -3.8, 95% CI -7.8 to 0.2) than unrecognized depressed participants. After 12 and 39 months, mean scores for both groups did not differ but were worse than those without depression. Conclusions. A minority of patients with MDD is recognized in primary care. Those who were unrecognized had comparable outcome after 12 and 39 months as participants with recognized depression.