Blood Cytokines IL-4 and MCP-3 Show Strong Links to Generalized Anxiety Disorder

Generalized anxiety disorder, one of the most common and persistent psychiatric conditions worldwide, may leave a measurable fingerprint in the blood. A new case-control study from Bangladesh reports that people with generalized anxiety disorder carry significantly lower levels of the anti-inflammatory signaling molecule interleukin-4 and markedly higher levels of the pro-inflammatory chemokine monocyte chemoattractant protein-3 compared with healthy individuals. The findings, published in Experimental Biology and Medicine, add fresh weight to the idea that anxiety is not purely a disorder of brain chemistry but also of immune regulation, and they point to two blood-borne molecules that could eventually serve as diagnostic biomarkers or drug targets.

The research team, led by scientists at the University of Asia Pacific and BRAC University in Dhaka, recruited 44 patients diagnosed with generalized anxiety disorder and 44 age- and sex-matched healthy controls. A professional psychiatrist evaluated all participants against DSM-5 criteria, and symptom severity was quantified using the widely used 7-item Generalized Anxiety Disorder scale, or GAD-7, which scores anxiety from minimal to severe on a 0-to-21 range. The researchers deliberately excluded anyone with other psychiatric conditions, chronic liver or kidney disease, acute or chronic infections, cancer, autoimmune disorders, recent use of anxiolytic or antidepressant medication, or pregnancy, because each of these factors could independently distort circulating cytokine levels and muddy the comparison.

Blood samples were drawn from each participant, allowed to clot, centrifuged to separate the serum, and stored at minus 80 degrees Celsius until analysis. The team then quantified interleukin-4 and MCP-3 concentrations using enzyme-linked immunosorbent assays, a standard laboratory technique in which antibodies capture the target molecule from the sample and a colorimetric reaction, read at 450 nanometers, reveals how much of it is present. Concentrations were calculated against standard curves and expressed in picograms per milliliter. Statistical comparisons relied on t-tests, chi-square tests for categorical data, Spearman correlation analysis, and receiver operating characteristic curve analysis to test how well each molecule could distinguish patients from controls.

The results were striking. Patients with generalized anxiety disorder had serum interleukin-4 concentrations averaging 11.82 picograms per milliliter, less than half the 24.51 picograms per milliliter measured in healthy controls. MCP-3 moved in the opposite direction, averaging 57.80 picograms per milliliter in patients versus 34.01 in controls. Both differences were highly statistically significant, with p-values below 0.001. Crucially, the two molecules also tracked symptom severity: interleukin-4 levels correlated negatively with GAD-7 scores, with a correlation coefficient of minus 0.496, while MCP-3 correlated positively with a coefficient of 0.544. In other words, the more severe the anxiety, the lower the anti-inflammatory signal and the higher the pro-inflammatory one.

Interleukin-4 is a cytokine produced primarily by Th2 helper T cells, and it acts as a molecular brake on inflammation. It suppresses the production of inflammatory mediators such as interleukin-1, interleukin-6, tumor necrosis factor-alpha, interleukin-8, and MCP-3 itself, while boosting natural anti-inflammatory regulators like the interleukin-1 receptor antagonist. In the brain, interleukin-4 has a well-documented neuroprotective role: it nudges resident immune cells called microglia away from the classically activated M1 state, which pumps out pro-inflammatory cytokines, and toward the alternatively activated M2 state, which releases anti-inflammatory molecules such as TGF-beta and interleukin-10 and helps resolve tissue damage. Animal studies have shown that this M1-to-M2 switching, mediated through the JAK1/STAT6 signaling pathway, protects the brain after injury. A deficit of interleukin-4, the authors argue, could therefore remove a key counterweight to neuroinflammation in brain regions that govern fear and worry.

MCP-3, by contrast, belongs to the CC chemokine family, a group of signaling proteins that guide immune cells to sites of inflammation through a process called chemotaxis. Structurally and functionally similar to its better-known cousin MCP-1, MCP-3 is a potent attractant for monocytes, T cells, natural killer cells, basophils, eosinophils, and dendritic cells. It exerts these effects by binding to the CCR2 receptor, found abundantly on monocytes and activated lymphocytes, and also to the CCR1 receptor. Studies in genetically engineered mice lacking MCP-3 have confirmed that the chemokine is a key driver of monocyte recruitment to inflamed tissue. Elevated MCP-3 in anxiety patients thus suggests an active mobilization of inflammatory cells, consistent with the hypothesis that chronic low-grade inflammation feeds into the biology of persistent worry.

The diagnostic potential of the two molecules was assessed with receiver operating characteristic analysis, which plots sensitivity against specificity across different cutoff values. MCP-3 emerged as the stronger performer, achieving an area under the curve of 0.848, with 87.6 percent sensitivity and 84.3 percent specificity at a cutoff of 45.0 picograms per milliliter. Interleukin-4 performed respectably but less impressively, with an area under the curve of 0.782, 80.2 percent sensitivity, and 78.5 percent specificity at a cutoff of 15.0 picograms per milliliter. An area under the curve approaching 0.85 is generally considered good discrimination, meaning a single blood test for MCP-3 could potentially flag a substantial majority of true anxiety cases while correctly clearing most healthy people, though it would not replace clinical assessment on its own.

The findings fit within a broader and sometimes contradictory literature. Preclinical work has repeatedly shown that injecting pro-inflammatory cytokines such as interleukin-1beta, interleukin-6, or tumor necrosis factor-alpha into animals induces anxiety-like behavior, and that this effect can be reversed by anti-inflammatory cytokines like interleukin-4 and interleukin-10. Clinical studies have often reported elevated pro-inflammatory and reduced anti-inflammatory cytokines in anxious patients, although some studies have found no differences or even lowered pro-inflammatory signals, highlighting how inconsistent the field remains. The cytokine hypothesis of anxiety proposes that pro-inflammatory molecules reduce serotonin production or increase its reuptake, thereby disturbing the serotonergic signaling that current medications like selective serotonin reuptake inhibitors are designed to enhance. Notably, roughly half of patients with generalized anxiety disorder do not respond adequately to existing drugs, and symptoms recur in at least 30 percent, underscoring the need for new mechanistic angles.

The study’s authors also see therapeutic potential in the interleukin-4/MCP-3 axis. Anti-cytokine monoclonal antibodies are already transforming the treatment of autoimmune diseases: secukinumab, ixekizumab, and bimekizumab block interleukin-17A, while ustekinumab targets interleukin-23A, and these agents are used in inflammatory bowel disease, psoriatic arthritis, and rheumatoid arthritis. If the same logic applies to anxiety, drugs that restore interleukin-4 signaling or dampen MCP-3-driven monocyte recruitment could one day complement or improve upon existing anxiolytics. The authors caution, however, that the immune system is finely balanced and that any such approach would require a deep understanding of which immune processes actually drive the disorder rather than merely accompany it.

Important limitations temper the excitement. The sample of 88 participants is small and drawn from a single Bangladeshi clinical setting, so the results may not generalize to other populations. As a case-control design, the study can demonstrate association but not causation; it remains unclear whether immune dysregulation contributes to causing anxiety, whether anxiety itself alters immune function, or whether both are driven by a third factor. The researchers also lacked detailed records of psychopharmacological treatment, and since antidepressants can themselves modulate inflammatory pathways, this absence may have confounded the observed associations. Sociodemographic differences in economic status and family history between the groups further complicate interpretation. The authors call for longitudinal studies with comprehensive medication histories to clarify the temporal dynamics of immune dysregulation as generalized anxiety disorder develops and progresses. Until then, the study stands as a compelling piece of evidence that the blood carries echoes of the anxious mind, and that measuring those echoes may one day help clinicians detect, grade, and treat one of the world’s most burdensome psychiatric conditions.

Subject of Research: Association of serum interleukin-4 and monocyte chemoattractant protein-3 levels with generalized anxiety disorder

Article Title: Altered serum interleukin-4 and monocyte chemoattractant protein-3 levels are associated with generalized anxiety disorder: a case-control study

Article References: Binta Rashid, M. H., Islam, M., Ashraful Islam, S. M., & Islam, M. R. (2026). Altered serum interleukin-4 and monocyte chemoattractant protein-3 levels are associated with generalized anxiety disorder: a case-control study. Experimental Biology and Medicine, 251, Article 11144. https://doi.org/10.3389/ebm.2026.11144

Image Credits: AI Generated

DOI: 10.3389/ebm.2026.11144

Keywords: generalized anxiety disorder, interleukin-4, MCP-3, cytokines, neuroinflammation, biomarkers, ELISA, ROC analysis, immune dysregulation, case-control study, microglia, anxiety severity