Executive Function Impairment in Unipolar vs Bipolar Depression

People with bipolar depression and unipolar depression who are not receiving medication experience similar impairments in executive function, according to study results published in the Journal of Affective Disorders.

People with bipolar depression (n=30) or unipolar depression (n=30) who were not receiving medication were recruited from the division of mood disorders at the Shanghai Mental Health Center. An additional 30 healthy controls were also included in the study. Patients in each group were assessed for symptoms of anxiety, depression, and mania. Executive function was evaluated using the Stroop color-word test and the Wisconsin Card Sorting Test. There were no significant differences in sociodemographic characteristics among patients in any group.

Compared with those who had unipolar depression, patients with bipolar depression experienced more mood episodes (P <.001), more depressive episodes (P =.021), and longer total episode duration (P =.002). However, there were no significant differences in duration of current depressive episode among these groups, nor in anxiety, depression, or mania scale scores. On the Stroop color-word test, the number of missing values was higher for both the bipolar depression group (P =.047) and the unipolar depression group (P <.05) than for the healthy control group. The unipolar depression group also had a lower number of correct values than the healthy control group (P <.05). On the Wisconsin Card Sorting Test, the percentage of errors and perception of conceptual level responses were worse in the unipolar depression group compared with the bipolar depression group (both P <.05). For patients with unipolar depression, executive function indices were correlated with the number of mood episodes (P <.01). The executive function of patients with bipolar depression, however, was associated instead with the duration of current depressive episode (P =.019) rather than with the number of mood episodes.  

These results suggest that executive function impairments may be similar for people with unipolar and bipolar depression. Such data provide perspective on each illness course and may assist clinicians in understanding the impact of depressive symptoms on psychosocial function.

Reference

Yang T, Zhang G, Mao R. The association of duration and severity of disease with executive function: differences between drug-naïve patients with bipolar and unipolar depression. J Affect Disord. 2018;238:412-417.