Differences in brain functioning between obsessive-compulsive disorder and generalized anxiety disorder: a clinical...

Generalized anxiety disorder (GAD) and obsessive-compulsive disorder (OCD) share common epidemiological and clinical features, but their shared neurobiological basis remains unclear. This study was designed to examine similarities and differences in brain functioning between GAD and OCD using functional near-infrared spectroscopy (fNIRS). 31 patients diagnosed with GAD, 31 with OCD, and 31 healthy controls (HCs) participated in the study. A 53-channel fNIRS system was used to measure changes in oxygenated hemoglobin ([oxy-Hb]) concentration during a verbal fluency task. Five regions of interest (ROIs) were defined: premotor cortex/supplementary motor area (SMA), Broca's area, dorsolateral prefrontal cortex (DLPFC), frontal eye fields (FEF), and frontopolar area (FPA). Using channel-based and ROI-based analysis strategies, [oxy-Hb] changes across groups were compared via one-way ANOVA and post hoc tests. HCs exhibited significantly greater brain activation in multiple regions (DLPFC, prefrontal cortex [PFC], Broca's area) than both patient groups. Post hoc analysis revealed that GAD patients showed higher activation in the left DLPFC and left FPA compared to OCD patients. Correlation analysis indicated that activation in the left Broca's area was significantly negatively correlated with obsessive-compulsive symptoms. Receiver operating characteristic (ROC) curve analysis demonstrated that the right FPA [oxy-Hb] value optimally discriminated patient groups (OCD and GAD) from HCs (optimal cutoff: 92.94505; sensitivity: 0.643; specificity: 0.816; AUC: 0.769 [95% CI: 0.661-0.877; *p* < 0.001]). These findings suggest that while GAD and OCD share overlapping neurofunctional alterations, OCD patients showed more marked deficits in the left DLPFC and left FPA.