Cited by 117Tryptophan and brain disordersGenetic Associations and EpidemiologyStress Responses and Cortisol

Depression and Interleukin-6 Signaling: A Mendelian Randomization Study

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Kelly, Kristen M., Smith, Jennifer A., Mezuk, Briana·2021·Brain, Behavior, and Immunity

Abstract

BACKGROUND: A large body of research has reported associations between depression and elevated interleukin-6 (IL-6), a cytokine with several roles including pro-inflammatory signaling. The nature and directionality of this relationship are not yet clear. In this study we use Mendelian Randomization to examine the possibility of a causal relationship between IL-6 and depressive symptoms, and to explore multiple signaling pathways that could serve as mechanisms for this relationship. METHODS: This study uses a two-sample Mendelian Randomization design. Data come from the UK Biobank (n = 89,119) and published summary statistics from six existing GWAS analyses. The primary analysis focuses on the soluble interleukin-6 receptor (sIL-6R), which is involved in multiple signaling pathways. Exploratory analyses use C-reactive protein (CRP) and soluble glycoprotein 130 (sgp130) to further examine potential underlying mechanisms. RESULTS: Results are consistent with a causal effect of sIL-6R on depression (PCA-IVW Odds Ratio: 1.023 (95% Confidence Interval: 1.006-1.039), p = 0.006). Exploratory analyses demonstrate that the relationship could be consistent with either decreased classical signaling or increased trans signaling as the underlying mechanism. DISCUSSION: These results strengthen the body evidence implicating IL-6 signaling in depression. When compared with existing observational and animal findings, the direction of these results suggests involvement of IL-6 trans signaling. Further study is needed to examine whether IL6R genetic variants might influence IL-6 trans signaling in the brain, as well as to explore other potential pathways linking depression and inflammation.

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Crossref · 10.1016/j.bbi.2021.02.019

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  • In depressed patients, sIL-6R levels were reported increased, with elevated levels of both IL-6 and sIL-6R persisting after the start of antidepressant treatment.

    “In addition to increased IL-6 levels, sIL-R6 levels were reported in depressed patients, with elevated levels of both persisting even after the start of antidepressant treatment [87,88].”

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Authors
Kelly, K. M., Smith, J. A., & Mezuk, B.
Affiliations
University of Michigan (US)
Corresponding author
Kelly, Kristen M.
Venue
Brain, Behavior, and Immunity
Publisher
Elsevier BV
Published
2021-07
Volume
95
Pages
106-114
ISSN
0889-1591 (ISSN-L)
OpenAlex
W3132094446
Cited by
117
References
90
Citations by year
2026: 23 · 2025: 22 · 2024: 34 · 2023: 20 · 2022: 15 · 2021: 3
FWCI
5.97
Type
journal article
Language
en
Open access
Locations
  • Brain Behavior and Immunity (publishedVersion, cc-by-nc-nd)
  • PubMed (publishedVersion)
  • VU Research Portal (publishedVersion, other-oa)
  • PubMed Central (acceptedVersion)
  • Data Archiving and Networked Services (DANS) (submittedVersion, other-oa)
Funders
  • National Institute of Mental Health (K01-MH093642-A1, 41812)
  • University of Michigan (T32-HG00040)
  • National Institutes of Health
  • National Human Genome Research Institute (T32-HG00040)
Topics
  • Life Sciences › Neuroscience › Biological Psychiatry › Tryptophan and brain disorders
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Genetic Associations and Epidemiology
  • Life Sciences › Neuroscience › Behavioral Neuroscience › Stress Responses and Cortisol
Keywords
depression, interleukin-6, IL-6 signaling, soluble IL-6 receptor, trans-signaling, C-reactive protein, soluble glycoprotein 130, inflammation, causal relationship, genetic variants
MeSH terms
Animals, Depression, Interleukin-6, Receptors, Interleukin-6, Cytokine Receptor gp130, Mendelian Randomization Analysis

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