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Causal relationships between somatic movement, brain structures, and mental well-being: A multi-stage Mendelian randomization study

Published online by Cambridge University Press:  10 April 2026

Lixin Guo
Affiliation:
Department of Radiology, The First Affiliated Hospital of Anhui Medical University, Hefei, China Research Center of Clinical Medical Imaging, Anhui Province, Hefei, China Anhui Provincial Key Laboratory for Brain Bank Construction and Resource Utilization, Hefei, China
Yuhao Shen
Affiliation:
Department of Radiology, The First Affiliated Hospital of Anhui Medical University, Hefei, China Research Center of Clinical Medical Imaging, Anhui Province, Hefei, China Anhui Provincial Key Laboratory for Brain Bank Construction and Resource Utilization, Hefei, China
Jie Wen
Affiliation:
Department of Radiology, The First Affiliated Hospital of Anhui Medical University, Hefei, China Research Center of Clinical Medical Imaging, Anhui Province, Hefei, China Anhui Provincial Key Laboratory for Brain Bank Construction and Resource Utilization, Hefei, China
Kaijie An
Affiliation:
Department of Radiology, The First Affiliated Hospital of Anhui Medical University, Hefei, China Research Center of Clinical Medical Imaging, Anhui Province, Hefei, China Anhui Provincial Key Laboratory for Brain Bank Construction and Resource Utilization, Hefei, China
Dan Zhang
Affiliation:
Department of Radiology, The First Affiliated Hospital of Anhui Medical University, Hefei, China Research Center of Clinical Medical Imaging, Anhui Province, Hefei, China Anhui Provincial Key Laboratory for Brain Bank Construction and Resource Utilization, Hefei, China
Xufeng Zhao
Affiliation:
Department of Radiology, The First Affiliated Hospital of Anhui Medical University, Hefei, China Research Center of Clinical Medical Imaging, Anhui Province, Hefei, China Anhui Provincial Key Laboratory for Brain Bank Construction and Resource Utilization, Hefei, China
Wenwei Zhang
Affiliation:
Department of Radiology, The First Affiliated Hospital of Anhui Medical University, Hefei, China Research Center of Clinical Medical Imaging, Anhui Province, Hefei, China Anhui Provincial Key Laboratory for Brain Bank Construction and Resource Utilization, Hefei, China
Jiajia Zhu*
Affiliation:
Department of Radiology, The First Affiliated Hospital of Anhui Medical University, Hefei, China Research Center of Clinical Medical Imaging, Anhui Province, Hefei, China Anhui Provincial Key Laboratory for Brain Bank Construction and Resource Utilization, Hefei, China
Yinfeng Qian*
Affiliation:
Department of Radiology, The First Affiliated Hospital of Anhui Medical University, Hefei, China Research Center of Clinical Medical Imaging, Anhui Province, Hefei, China Anhui Provincial Key Laboratory for Brain Bank Construction and Resource Utilization, Hefei, China
*
Corresponding authors: Jiajia Zhu and Yinfeng Qian; Emails: zhujiajiagraduate@163.com; liangminqyf@sohu.com.
Corresponding authors: Jiajia Zhu and Yinfeng Qian; Emails: zhujiajiagraduate@163.com; liangminqyf@sohu.com.
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Abstract

Background

While the relationships between somatic movement, mental well-being, and brain health have been well established, the causal nature and underlying mechanisms of such associations remain incompletely understood.

Methods

By applying multi-stage Mendelian randomization to multi-source summary data derived from genome-wide association studies, we examined the causal effects of 4 somatic movement measures on 2 mental well-being indices and 13 types of brain structures, followed by testing the mediating roles of brain structures in accounting for the causal associations between somatic movement and mental well-being.

Results

Two-sample Mendelian randomization revealed that more physical activity was causally associated with greater mental well-being (life satisfaction and positive affect), while more sedentary behavior (longer leisure screen time and more sedentary behavior at work) with lower mental well-being. With respect to brain structures, sedentary behavior was causally linked to decreased volume, surface area, and local gyrification index in distributed cortical regions. Remarkably, decreased surface area of the piriform cortex was found to mediate the causal associations between sedentary behavior and lower mental well-being.

Conclusions

Our findings not only complement and extend earlier reports on the associations of somatic movement with mental well-being and brain health by further resolving the causality but also help elucidate the neural mechanisms by which sedentary behavior adversely affects mental well-being.

Information

Type
Original Article
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© The Author(s), 2026. Published by Cambridge University Press
Figure 0

Figure 1. Overview of the multi-source GWAS data integration and the different levels of MR analyses. Abbreviations: GWAS, genome-wide association study; IV, instrumental variable; IVW, inverse variance weighted; MAF, minor allele frequency; MR, Mendelian randomization; SNP, single-nucleotide polymorphism.

Figure 1

Figure 2. Causal effects of somatic movement on mental well-being. Abbreviations: CI, confidence interval; IVW, inverse variance weighted; LS, life satisfaction; LST, leisure screen time; MR, Mendelian randomization; MVPA, moderate-to-vigorous intensity physical activity during leisure time; PA, positive affect; SDW, sedentary behavior at work.

Figure 2

Figure 3. Causal effects of somatic movement on brain structures. Color represents β coefficient. Abbreviations: IVW, inverse variance weighted; LST, leisure screen time; MR, Mendelian randomization; SDW, sedentary behavior at work.

Figure 3

Figure 4. Mediating role of brain structure in the causal associations between somatic movement and mental well-being. (A) Causal effects of brain structure on mental well-being. (B) Two causal mediating pathways from somatic movement to mental well-being through brain structure. Abbreviations: CI, confidence interval; IVW, inverse variance weighted; LS, life satisfaction; LST, leisure screen time; MR, Mendelian randomization; PA, positive affect; Pir, piriform cortex; SA, surface area.

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