Handgrip and gait metrics as scalable markers of physical health in schizophrenia and alcohol use disorders.

Schizophrenia (SCZ) and alcohol use disorder (AUD) are associated with physical decline and motor dysfunction, but objective wearable-based motor assessments remain underutilized in psychiatric research. This study compared handgrip strength (HGS) and gait features between healthy controls (HCs) and individuals with SCZ or AUD using wearable sensors. A total of 434 participants (HCs: n = 210; AUD: n = 80; SCZ: n = 144) completed instrumented Timed Up and Go, walking, and HGS tests. Fifteen motor features were extracted and analyzed using multivariable linear regression adjusted for age, sex, and BMI. Five features-HGS, relative HGS (rHGS), walk quality index, symmetry index, and mid-turning phase duration-significantly differentiated one or both diagnostic groups from HCs. In AUD, rHGS showed moderate associations with multiple gait parameters, consistent with more widespread motor dysfunction. In SCZ, these associations were weaker, suggesting reduced coupling between upper- and lower-limb motor function. Both groups showed reduced HGS and gait alterations, but with distinct coordination patterns. These findings support wearable-based grip and gait metrics as scalable and objective motor functional markers in SCZ and AUD.