Performance on the Wechsler Adult Intelligence Scale (WAIS ) in Japanese patients with bipolar and major depressive disorders in euthymic and depressed states

Aim This study aimed to examine the cognitive performance of patients with bipolar disorder (BD) stratified by illness phase compared to that of patients with major depressive disorder (MDD) and healthy controls. Methods Participants were 139 patients with BD (55 euthymic and 84 depressed), 311 patients with MDD (88 euthymic and 223 depressed), and 386 healthy controls who underwent the Wechsler Adult Intelligence Scale‐Revised or the Third Edition. They were non‐elderly Japanese individuals with normal estimated premorbid intelligence quotient (IQ; >90), group‐matched for age, sex, and premorbid IQ. Results The depressed BD group showed significantly lower scores on verbal IQ, performance IQ, full‐scale IQ, and three group indexes of perceptual organization, working memory, and processing speed when compared with healthy controls (all P