IL6 and major depressive disorder: Analyses, such as in the Netherlands Study of Depression and Anxiety, show linear increases in inflammatory markers like CRP (P = .026) and IL-6 (P = .090) across clinical stages, with changes also evident in at-risk individuals (IL-6, P = .050).[1] Neurotransmitter dysregulation, including autonomic imbalance reflected in abnormal heart rate variability (HRV), is another key feature.