Altered Serum IL-6 and TGF-β1 Levels Are Associated With Generalized Anxiety Disorder: A Case-Control Study

Generalized anxiety disorder (GAD) is a chronic psychiatric disease characterized by excessive and uncontrollable worry about common life events. Neurological, neurochemical, genomic, environmental, psychogenic, and immunological factors are thought to be involved in GAD. However, studies conducted to establish any suitable biomarkers for the assessment of anxiety disorder is limited. Hence, we aim to investigate the serum levels of interleukin-6 (IL-6) and transforming growth factor-beta 1 (TGF-β1) in GAD patients.

The present study enrolled 44 GAD patients and 44 healthy controls (HCs) from a tertiary care teaching hospital in Dhaka, Bangladesh. A qualified psychiatrist assessed the study population based on the criteria mentioned in the DSM-5. We measured the serum levels of IL-6 and TGF-β1 using the commercially available enzyme-linked immunosorbent assay (ELISA) kits.

We noted a significant reduction in serum IL-6 and TGF-β1 levels in GAD patients compared to HCs (IL-6: 7.72 ± 2.14 vs. 9.39 ± 1.22 pg/mL; p = 0.003, and TGF-β1: 386.77 ± 157.91 vs. 774.51 ± 327.73 pg/mL; p = 0.001). Moreover, a significant negative association was found between the levels of IL-6 and GAD-7 scores among the GAD patients (r = -0.395, p < 0.001). Lastly, the ROC analysis demonstrated a strong predictive accuracy with a moderately higher area under the curve (AUC) value (IL-6: 0.888 and TGF-β1: 0.891), relatively higher sensitivity (IL-6: 85.3% and TGF-β1: 85.6%), and higher specificity (IL-6: 86.7% and TGF-β1: 82.4%).

Our study findings underscore that lowered IL-6 and TGF-β1 levels might have a role in the pathophysiology and development of GAD. Therefore, the alterations of cytokines have a crucial role in evaluating the GAD patients. We suggest further interventional studies to determine the actual predictive performance of IL-6 and TGF-β1 in GAD.