Subthreshold bipolarity common in major depressive disorder

By Mark Cowen, Senior medwireNews Reporter

Results from a Polish study show that a substantial proportion of patients with major depressive disorder meet criteria for subthreshold bipolarity.

J Raybakowski (Poznan University of Medical Sciences) and colleagues found that up to 37% of patients with a first or recurrent unipolar major depressive episode had subthreshold bipolarity, depending on the assessment tool used.

In addition, the researchers also found that such patients were more likely to be resistant to treatment with antidepressants than those without subthreshold bipolarity.

"The results confirm a substantial percentage of bipolarity in major depressive disorder," they comment in European Psychiatry.

The findings come from a study of 1051 patients (299 mean), aged 18‑77 years, from 16 regions of Poland who were diagnosed with a first or recurrent unipolar major depressive episode according to International Classification of Diseases-10 criteria.

All of the participants were assessed for subthreshold bipolarity using the Hypomania Checklist (HCL-32) and the Mood Disorder Questionnaire (MDQ).

The team found that 37.7% of the patients exceeded the subthreshold bipolarity cutoff score of 14 on the HCL-32 and 20.0% exceeded the bipolarity cutoff of 7 on the MDQ.

In addition, patients with subthreshold bipolarity according to the HCL-32 were more likely to be resistant to treatment with antidepressants than those without, at 43.9% versus 30.0%, as were those with subthreshold bipolarity according to the MDQ than those without, at 26.4% versus 12.4%.

Overall, patients who met criteria for subthreshold bipolarity on either of the assessment tools were less likely to be married, had an earlier age at onset, a greater number of depressive episodes and psychiatric hospitalizations, and were more likely to have a history of suicidal behaviour and alcoholism, and a family history of depression than those who did not have subthreshold bipolarity.

Raybakowski et al conclude: "The results obtained in this study confirm a substantial percentage of subthreshold bipolarity in major depressive disorder.

"Furthermore, they corroborate other results indicating an association between the features of bipolarity and more severe character of the illness as well as between the bipolarity and the refractoriness of depression to treatment with antidepressant drugs."

Licensed from medwireNews with permission from Springer Healthcare Ltd. ©Springer Healthcare Ltd. All rights reserved. Neither of these parties endorse or recommend any commercial products, services, or equipment.