All group differences were corrected using the GRF method (voxel level p < 0.001, cluster level p < 0.05). The stages in the main grouping strategy were categorized using the illness duration of GAD (stage 1, 0–3 years; stage 2: 4–20 years) (a). The stages in the validation grouping strategy were separated using the illness duration of GAD (stage 1, 0–2 years; stage 2, 3–5 years; stage 3, 6–20 years) (b). GMV gray matter volume, GAD generalized anxiety disorder.