The vagus nerve acts as the primary parasympathetic regulator of immune function, and higher vagal tone is associated with reduced sympathetic dominance and lower systemic inflammation.

Study: Parasympathetic neural activity and the reciprocal regulation of innate antiviral and inflammatory genes in the human immune system

This study shows that when your vagus nerve is more active (measured by heart rate patterns), your body produces less inflammation and more antiviral defenses — meaning a calm nervous system helps your immune system fight sickness better.

Study: Vagal Nerve Stimulation-Modulation of the Anti-Inflammatory Response and Clinical Outcome in Psoriatic Arthritis or Ankylosing Spondylitis

This study showed that gently stimulating the vagus nerve with a device reduced inflammation in people with joint diseases, proving that this nerve helps calm the immune system. When the vagus nerve is activated, the body’s inflammatory response goes down.

Study: Stress and Heart Rate Variability: A Meta-Analysis and Review of the Literature

This study shows that when people are stressed, their body’s calming system (controlled by the vagus nerve) slows down, which makes their stress system run too hard — and that can lead to more inflammation. So yes, it supports the idea that a weak vagus nerve means more stress and inflammation.