In African‐American patients with psycho‐affective or schizophrenic disorders, the TCF7L2 rs7903146‐T variant was associated with T2D (OR = 1.4; p = 0.03) by the additive model, and more so by the recessive model (OR = 2.4; p = 0.004). Here, TCF7L2 is linked to type 2 diabetes mellitus.