The social dimension of apathy: Evidence for a distinct domain from 11,243 individuals across health and neurocognitive disorders

Apathy is a highly prevalent and disabling neuropsychiatric syndrome, but its multi-dimensional structure is a challenge for progress towards better identification and treatment. A critical question is whether social disengagement reflects a distinct deficit in social motivation or a by-product of diminished initiative or emotional blunting. Previous studies have been constrained by modest sample sizes and limited use of apathy-specific instruments or phenotypically narrow cohorts. Here, we examined data from 11,243 individuals recruited across multiple centres, including 1,154 neurological patients with Alzheimer's disease, Parkinson's disease, frontotemporal dementia, autoimmune encephalitis and small vessel disease, alongside people with depression and healthy adults. Across exploratory and confirmatory factor analyses, symptom-level network modelling, and lifespan analyses, social apathy consistently emerged as a coherent and separable dimension. The pattern was stable across health, depression, and neurocognitive disorders, and evident from adolescence to late life. These findings suggest that social apathy is a distinct and stable component of apathy. Recognising this domain has important implications for diagnostic nosology, for probing the underlying cognitive process that leads to apathy, and its structural correlates, leading ultimately to better targeted psychosocial and pharmacological interventions.