The effect of comorbid anxiety disorder on neuropsychological function in bipolar II disorder

Objectives: Bipolar disorder (BP) is often comorbid with anxiety disorder (ANX), especially in bipolar II disorder (BP-II). BP patients with comorbid ANX often manifest intensified symptoms and harmful dysfunctions. However, most studies have focused on bipolar I disorder (BP-I); few have investigated the effect of comorbid ANX on the neuropsychological function of BP-II patients. We examined neuropsychological functions in BP-II patients with and without comorbid ANX. Methods: Fifty-nine participants were recruited: 20 patients with interepisode (symptom-free) BP-II without comorbid ANX, 20 with interepisode BP-II with comorbid ANX, and 19 healthy controls. All participants were screened using the Chinese version of the Modified Schedule of Affective Disorder and Schizophrenia-Lifetime (SADS-L). Individuals comorbid with major or minor mental illness other than BP-II were excluded. Comparisons were made between the three groups using neuropsychological tests to assess memory, attention, psychomotor speed, and frontal executive function. Results: BP-II patients with comorbid ANX showed poorer neuropsychological functions than those in the BP-II-only and control groups. Additionally, BP-II-only patients and controls showed equal cognitive performance. Conclusions: Because BP-II patients with comorbid ANX had the lowest scores in the majority of neuropsychological functional tests, we conclude that they have greater cognitive impairments than do BP-II patients without comorbid ANX. Neuropsychological dysfunctions seemed more strongly associated with ANX than with BP-II in interepisode periods. Identifying and managing ANX comorbidity is critical when treating BP-II patients.