highly significantp < 0.001
The group × age interactions were negative and highly significant for both BD ( β = −0.51, t = −4.63, p < 0.001) and SZ ( β = −0.48, t = −4.26, p < 0.001), indicating steeper age‐related decline relative to HC, that is, an early elevation in Brain–PAD followed by age‐related normalization.