Question:  Can handgrip strength provide an indication of cognitive functioning in people with major depression or bipolar disorder and healthy controls? Findings: In this cross-sectional analysis of a population-scale data set of 110 067 individuals, handgrip strength was significantly associated with all 5 domains of cognition in people with major depression and in healthy controls, independently of confounding factors. Similar associations, but to a lesser extent, were observed in those with bipolar disorder. Meaning:  Handgrip strength is associated with overall cognition in individuals with and without major depression; muscular function may provide a proxy for assessing neurocognitive impairment and present a novel interventional outcome for targeting cognitive improvement.. Please contact the library to request a copy of this article - http://bit.ly/1Xyazai