Treatment received by depressed patients in Japan and its determinants: naturalistic observation from a multi-center collaborative follow-up study

Background: Undertreatment of depression appears widespread but the available literature is limited to North American and European countries. We aimed to examine the treatment received by patients with major depression in Japan and to elucidate any predictor of their treatment level. Methods: A naturalistic, prospective follow-up study of an inception cohort of subjects with mood disorders was undertaken in psychiatric departments of 13 university hospitals, those of six general hospitals, three mental hospitals and one community mental health center from all over Japan. A total of 95 patients without any prior antidepressant treatment were diagnosed with major depression according to DSM-IV and were followed up every month until treatment termination and every 6 months thereafter. Results: The follow-up information was available in 98 to 97% of the cohort. The proportion of patients receiving less than 125 mg/day of imipramine or equivalent reached 69% (95% CI: 58–78%) at 1 month and 67% (95% CI: 54–77%) at 6 months. A few clinical variables were significantly associated with inadequate antidepressant prescription but altogether they explained only 5 to 14% of the variance observed. Conclusions: Japan was no exception to the other industrialized countries in its less than optimal provision of treatment to major depression and its lack of explanatory predictors for this common practice.