Bipolarity in treatment-resistance depression-preliminary results from the TRES-DEP study

Objective: The study aimed to analyse the bipolarity features between patients with treatment-resistant depression and patients with remission of a depressive episode.

Methods: The population studied included patients aged 18-65 who had a diagnosis of first or recurrent major depressive disorder. Each psychiatrist included 5 consecutive patients, from all the patients he is treating, where the depressive episode was assessed as treatment-resistant (TR) and 5 consecutive patients with a depressive episode in remission (RE). One thousand and fifty-one patients entered the study: 570 in the treatment-resistant depression group and 481 in the remission group. All patients were assessed using the Mood Disorder Questionnaire (MDQ) and Hypomania Checklist (HCL-32). The assessment of current depressive symptoms was done by means of a 17-item Hamilton Depression Rating Scale.

Results: The percentage of patients screened positive by MDQ was significantly higher in TR than in RE (13.7 vs. 5.6% p < 0.001). Also, the percentage of patients having positive response to 14 or more items of the HCL-32 was significantly higher in TR than in RE (43.9% vs. 30.0%, respectively, p < 0.001). The multiple logistic regression model showed that independent risk factors for treatment resistance were: bipolar features in HCL-32 scale, scoring 6 or higher on MDQ, age at first onset < or = 20 years, more than three previous depressive episodes and partial remission after the previous depressive episode.

Conclusions: Identified independent risk factors for treatment resistance suggest possible association between bipolarity and worse response to antidepressant drugs in patients with mood disorders.