Psychopathological Features of Treatment-Resistant Unipolar Depression

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Clinical and socio-demographical characteristics between bipolar I disorder, bipolar II disorder, and treatment-resistant unipolar depression were examined.

Treatment-resistant unipolar depression should not be considered a prodromal state of bipolar depression, as it has distinct psychopathological features, according to a recent study published in BMC Psychiatry.  

This observational, retrospective, cross-sectional chart review study examined the demographic and clinical characteristics that had been previously described as predictors or risk factors for treatment-resistant unipolar and bipolar depression. Researchers were seeking to find characteristics that differentiated treatment-resistant unipolar depression from depressive episodes in bipolar depression spectrum disorders. They also investigated the differences between the sociodemographic and clinical characteristics of bipolar depression types I and II, and those of treatment-resistant unipolar depression.

The charts were collected from the Patient Registry at the McGill University Health Center’s Mood Disorders Clinic (MDC). The MDC Patient Registry is a research database of information on all individuals with bipolar depression and unipolar depression who were treated/followed at the MDC for more than 2 years, with a mean of 7.5 years. The study focused on 194 registrants between 19 and 75 years (mean age 43.6, ±14.1) with a unipolar depression or bipolar depression diagnosis who met the criteria for a major depressive episode according to the DSM-IV. Charts for 100 individuals met the criteria for treatment-resistant unipolar depression and 94 met the criteria for bipolar depression. Out of those with bipolar depression, 42 had bipolar depression II and 52 had bipolar depression I. Women made up 58.3% of the total sample, with 39.2% men.

Chart analysis using binary logistic regression revealed the different clinical predictors associated with treatment-resistant unipolar depression in comparison with bipolar depression. Individuals with treatment-resistant unipolar depression exhibited higher rates of anxiety, a greater degree of depression severity, lower global functioning scores, and fewer hospitalizations than those with bipolar depression. Secondary findings demonstrated that those with bipolar depression I show higher rates of hospitalizations and unemployment, but lower rates of suicide attempts when compared with those with bipolar depression II.

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Study investigators conclude that the distinct clinical features and histories of individuals with treatment-resistant unipolar depression compared with those with bipolar depression clearly indicate that these are separate psychopathological conditions requiring different treatment approaches, adding that “further studies are needed to differentiate the pharmacological responses and outcomes in these distinct groups.”


Nuñez NA, Comai S, Dumitrescu E, et al. Psychopathological and sociodemographic features in treatment-resistant unipolar depression versus bipolar depression: a comparative studyBMC Psychiatry. 2018; 18(1):68.