Background: 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.
Method: 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).
Results: 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.
Limitation: A retrospective assessment of treatment resistance.
Conclusions: 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.
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