Immune activity in the body may reach far beyond aching joints or a passing fever. The chronic low-grade inflammation that lingers in conditions such as rheumatoid arthritis, inflammatory bowel disease and obesity is increasingly connected to depression and anxiety.
Central to the idea are cytokines, the messenger molecules immune cells use to talk to one another. Some of these signals appear able to travel to the brain and shift how a person feels, thinks and sleeps.
A 2014 analysis of a UK birth cohort published in JAMA Psychiatry found that children in the highest third for interleukin-6 (IL-6) at age 9 were roughly 55 percent more likely to be depressed at 18 than those in the lowest third, with an adjusted odds ratio of 1.55.
The signal has since shown up in adult populations, too.
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How the immune system reaches the brain
Sustained exposure to cytokines like IL-6, TNF-α and IL-1β can activate inflammatory pathways inside the brain and disturb neurotransmitter systems that regulate mood, especially serotonin, dopamine and glutamate. That is the picture drawn by a 2023 review in Frontiers in Psychiatry by psychiatrist Sameer Hassamal of California University of Sciences and Medicine.
One well-studied route is the kynurenine pathway. Pro-inflammatory cytokines can trigger an enzyme that pulls tryptophan away from serotonin production toward compounds that act on brain circuits tied to fatigue, low motivation and blunted mood.
Peripheral inflammation may also loosen the blood-brain barrier and switch microglia, the brain's own immune cells, into a state that releases further cytokines and disrupts neurotransmission.
What autoimmune patients reveal
The largest population look at the link comes from Our Future Health, a UK cohort. In a study of more than 1.5 million adults published in BMJ Mental Health in June 2025, researchers reported that people with an autoimmune condition had a lifetime prevalence of depression or anxiety of 28.8 percent, compared with 17.9 percent in the general population.
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After adjusting for age, sex, ethnicity, income, parental history, chronic pain and social isolation, the odds of an affective disorder remained about 1.5 times higher in those with an autoimmune diagnosis.
The authors caution that the design cannot prove cause, but concluded that chronic exposure to systemic inflammation may be linked to a higher risk of depression and anxiety.
Where the evidence stops short
Anti-inflammatory drugs have shown small mood benefits in some trials, though the results fall well short of a treatment. A meta-analysis in the Journal of Clinical Medicine reported that adding the COX-2 inhibitor celecoxib, at 400 mg a day for six weeks, to standard antidepressants produced significantly greater symptom reduction than placebo in major depression. The trials were small and mostly short, and blood levels of the inflammation marker C-reactive protein did not reliably predict who improved.
Long-term use of NSAIDs like ibuprofen carries risks for the stomach, kidneys and cardiovascular system, and none of these drugs is approved as an antidepressant. Anyone with persistent low mood, sleeplessness or anxiety should speak with a physician rather than self-medicate.
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Daily habits still matter. A Mediterranean-style eating pattern rich in vegetables, fruits, whole grains, beans, nuts, fish and olive oil has been associated with lower inflammation and modest reductions in depressive symptoms across five randomized trials pooled in Nutrition Reviews in January 2024. Regular sleep, movement and not smoking act on the same everyday biology.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.