A unified general cognitive factor explains impairment across schizophrenia, bipolar disorder, OCD and substance use disorder

Background: Emerging evidence suggests that cognitive impairment cuts across traditional psychiatric diagnoses and may reflect a shared underlying cognitive liability. We examined whether a general cognitive factor (gFc) accounts for transdiagnostic deficits across schizophrenia (SZ), bipolar disorder (BD), obsessive-compulsive disorder (OCD) and substance use disorder (SUD). Methods: A total of 472 affected individuals and 253 population healthy controls (HC) completed a standardized cognitive battery. Bifactor confirmatory factor analysis was used to derive general cognitive factor (gFc) and domain-specific abilities(cognitive flexibility, working memory, new learning and social cognition). Model fit supported the bifactor structure. Linear mixed-effect models, with family as random effect, and demographic variables as fixed effect evaluated transdiagnostic and diagnosis specific impairments.. Results: The gFc was significantly reduced across all diagnoses groups relative to HC, [B(SE): BD -0.49 (0.07), OCD -0.21 (0.07), SUD -0.43(0.08), SZ -0.76 (0.08), all p < 0.001]; verbal learning showed additional diagnosis-specific deficits, most pronounced in SZ [B (SE): -0.59 (0.09)] and BD[B(SE): -0.48 (0.09)], both p