Associations between the fat mass and obesity-associated (FTO) gene and obesity are well-established. However, recent studies have linked FTO to addiction phenotypes and dopaminergic signaling, thus suggesting broader psychiatric implications. We explored this assumption by conducting a phenome-wide association study (PheWAS) across 4,756 genome-wide association studies (GWASs), identifying 26 psychiatric traits associated with FTO at the multiple-corrected significance level. These traits clustered into four categories: substance use, chronotype/sleep, well-being, and neuroticism. To validate these findings, we analyzed a functionally suggestive FTO variant (rs1421085) in a separate cohort, examining its impact on (i) alcohol use based on the Alcohol Use Disorders Identification Test (AUDIT), (ii) subjective well-being based on the WHO (Ten) Well-Being Index, and (iii) neuroticism based on Schafer's Five Factor Model (FFM) or the Karolinska Scales of Personality (KSP). Our results confirmed a direct association between rs1421085 and neuroticism that was independent of age, sex, alcohol use, body mass index (BMI), and childhood adversities. Interestingly, while no direct association with alcohol intake was observed, both cross-sectional and lagged longitudinal mediation analyses uncovered indirect relationships between rs1421085 and problematic alcohol use (AUDIT-P), with increased neuroticism acting as the intermediary. Mediation analyses also supported an indirect effect of rs1421085 on lower well-being through the pathways of increased neuroticism and BMI. Our study is the first to validate a direct association between FTO and neuroticism. However, additional studies are warranted to affirm the causal pathways linking FTO to well-being and alcohol use through neuroticism.

The authors have declared no competing interest.

This study was funded by the Royal Physiographic Society in Lund (42797, 2022; P.A.M.), the Ake Wiberg Foundation (M21-0092, 2021 and M22-0059, 2022; P.A.M.), the Magnus Bergvall Foundation (2021-04173, 2021 and 2022-038, 2022; P.A.M.), the Sigurd and Elsa Golje Memorial Foundation (LA2021-0124, 2021 and LA2022-0139; P.A.M.), the Swedish Brain Foundation (FO2023-0167; P.A.M. and 2023-0335; C.L.), the Karolinska Institutet Research Grants (2022-01667, 2022; P.A.M.), the regional agreement on medical training and clinical research (ALF) between Stockholm County Council and Karolinska Institutet Stockholm County Council (RS2021-0855, SLL20190589; C.L.), and the Swedish Research Council (2023-02253; P.A.M., and 2022-1188; C.L.).

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Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Ethics committee of the Karolinska Institutet gave ethical approval for this work

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All data produced in the present study are available upon reasonable request to the authors