However, we found significant positive correlations between plasma FGF21 levels and two subscales of the Brief Assessment of Cognition in Schizophrenia (BACS) in patients with BD; letter fluency and motor speed, thereby indicating that higher plasma FGF21 levels are potentially associated with improved cognitive functions in patients with BD. Plasma FGF21 levels were not correlated with depression severity assessed with HAM‐D. This evidence concerns the gene FGF21 and depressive disorder.