Steen, Olivier D, Ohlsson, Henrik, van Ockenburg, Sonja L et al. · Brain, behavior, and immunity · 2026 · DOI
A large Swedish study examined whether functional somatic syndromes (including ME/CFS, fibromyalgia, and IBS) and depression/anxiety share genetic risk factors with immune-mediated diseases. Researchers observed that fibromyalgia showed the strongest shared genetic risk with immune diseases, while ME/CFS showed more modest genetic overlap. The findings are preliminary and do not explain why these conditions cluster together, only that genetic factors may contribute to some shared risk.
For ME/CFS researchers, this study provides quantitative evidence that genetic risk factors are shared between ME/CFS and immune-mediated diseases—an observation that may inform future investigation of biological mechanisms. However, the modest genetic correlation (0.19–0.29) indicates that most of the variance in ME/CFS remains unexplained by immune genetic risk, suggesting other pathways warrant investigation.
This study does not establish that immune dysfunction causes ME/CFS, nor does it identify which specific genes or immune pathways contribute. Registry-based diagnoses may misclassify patients or miss milder cases. The genetic overlap does not confirm a shared mechanism—genetic factors could influence different pathways in different disorders. Cross-sibling data cannot resolve causality from shared environment.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Steen, Olivier D, Ohlsson, Henrik, van Ockenburg, Sonja L, Kendler, Kenneth S, Rosmalen, Judith G M, Sundquist, Kristina, et al. (2026). Shared genetic risk between functional somatic syndromes, internalizing disorders, and immune-mediated diseases: a twin-sibling study.. Brain, behavior, and immunity. https://doi.org/10.1016/j.bbi.2026.106837
BibTeX
@article{mecfsatlas-steen-2026-shared-genetic,
author = {Steen, Olivier D and Ohlsson, Henrik and van Ockenburg, Sonja L and Kendler, Kenneth S and Rosmalen, Judith G M and Sundquist, Kristina and van Loo, Hanna M},
title = {Shared genetic risk between functional somatic syndromes, internalizing disorders, and immune-mediated diseases: a twin-sibling study.},
journal = {Brain, behavior, and immunity},
year = {2026},
doi = {10.1016/j.bbi.2026.106837},
note = {PubMed: 42190845},
url = {https://www.mecfsatlas.com/evidence/steen-2026-shared-genetic},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-27. https://www.mecfsatlas.com/evidence/steen-2026-shared-genetic
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