Risk factors of treatment resistance in major depression: association with bipolarity

An undiagnosed and therefore inadequately treated bipolarity may be an important cause of drug resistance in depression diagnosed as unipolar. The study aimed to detect clinical and demographic characteristics, with a special interest in bipolarity features which could be risk factors for treatment resistance in unipolar depression.

One-thousand and fifty-one patients recruited from 150 outpatient psychiatric clinics and fulfilling DSM-IV criteria for major depressive episodes, single or recurrent, were studied. Among them, 569 patients with treatment-resistant depression (TR) were compared with 482 patients with non-treatment-resistant depression (NTR). All patients were assessed using the structured demographic and clinical data interviews, Mood Disorder Questionnaire (MDQ) and Hypomania Checklist (HCL-32).

Independent risk factors of treatment resistance were: scoring 6 or higher on MDQ, scoring 14 or higher in HCL-32, age at first onset < or = 20 years, more than three previous depressive episodes, and lack of remission or partial remission after the previous depressive episode.

A retrospective assessment of treatment resistance.

Bipolarity features as assessed by MDQ and HCL-32 were identified as significant factors of treatment resistance. Some other clinical variables connected with treatment resistance may be also be associated with bipolarity features.