Fig. 3

Mediation analysis testing whether GMV in bilateral insula mediates the relationship between BMI and negative symptoms in SZ. The age, sex, education, ICV, and duration of illness were included as covariates. A Standard 3-variable path model of mediation analysis. Path c is the total effect of X on Y; path c′ is the direct effect of X on Y after controlling for M; the product of paths a and b (a × b) is the indirect effect of X on Y through M. B Results from the bilateral insula identified in main effects of diagnosis: INS_L (left) and INS_R (right). C Results from the bilateral insula identified in main effects of BMI: INS_L1 (left) and INS_R1 (right). Unstandardized path coefficients are displayed along with standard errors in parentheses, and significance levels (ie, p value) underneath them. The total effects, direct effects, and indirect effects were considered significant when the p < 0.05 or 95% CIs did not contain zero. Note: GMV, gray matter volume; INS, insula; L, left; R, right; SZ, schizophrenia; OWB, overweight/obesity; ICV, total intracranial volume; BMI, body mass index; SE, standard errors; CIs, confidence intervals