Phenotypic and genetic associations between anhedonia and brain structure in UK Biobank

Background: Anhedonia is a core symptom of multiple psychiatric disorders and has been associated with changes in brain structure. Genome-wide association studies suggest that anhedonia is heritable with a polygenic architecture but few studies have explored the association between genetic loading for anhedonia - indexed by polygenic risk scores for anhedonia (PRS-anhedonia) - and structural brain imaging phenotypes. We investigated how anhedonia and polygenic risk for anhedonia were associated with brain structure within the UK Biobank cohort. Methods: Brain measures (including total grey/white matter volumes, subcortical volumes, cortical thickness and white matter integrity) were analysed in relation to the self-reported anhedonia phenotype and PRS-anhedonia for 17,492 participants (8,506 males and 8,986 females; mean age = 62.81 years, SD = 7.43), using linear mixed models and including mediation analyses. Results: State anhedonia was significantly associated with smaller total grey matter volume (GMV), smaller volumes in thalamus and nucleus accumbens; as well as reduced cortical thickness within the paracentral gyrus, the opercular part of inferior frontal gyrus and the rostral anterior cingulate cortex. PRS-anhedonia was associated with reduced total GMV, increased total white matter volume and reduced white matter integrity; in addition to reduced cortical thickness within the parahippocampal cortex, the superior temporal gyrus and the insula cortex. Conclusions: Both the state anhedonia phenotype and PRS-anhedonia were associated with differences in multiple brain structures/areas, including within reward-related circuits. These differences may represent vulnerability markers for psychopathology across a range of psychiatric disorders.