Shared and disorder-specific functional alterations in generalized anxiety disorder and major depressive disorder.

BACKGROUND: Generalized anxiety disorder (GAD) and major depressive disorder (MDD) show substantial clinical overlap, yet their shared and disorder-specific intrinsic functional abnormalities remain unclear. This study examined regional brain activity and whole-brain functional integration in GAD and MDD using resting-state fMRI. METHODS: Forty-two GAD patients, 43 MDD patients, and 83 healthy controls underwent resting-state fMRI. ALFF and FCS were calculated to assess regional spontaneous activity and whole-brain functional integration, respectively. Group differences were tested using voxel-wise ANCOVA controlling for age, sex, education, and frame-wise displacement. Partial correlations examined associations with clinical symptoms. RESULTS: Both patient groups showed decreased ALFF in a cluster spanning the left precuneus and right cuneus, with lower ALFF in GAD than in MDD. Both groups also showed decreased FCS in the bilateral lingual gyri, right middle occipital gyrus, and left postcentral gyrus, and increased FCS in the right inferior frontal gyrus. GAD showed lower FCS in the left lingual gyrus than MDD. CONCLUSIONS: GAD and MDD showed shared functional alterations in posterior cortical, visual, somatosensory, and frontal regions, while GAD exhibited lower ALFF and FCS in specific posterior cortical regions than MDD.