@leanguy 138 wrote:

Is there a connection between an “overactive” immune system and anxiety? Is inflammation to blame?

There is a connection between immune system overactivity and anxiety and inflammation.

There are bidirectional connections between the nervous system, endocrine system, and immune system. To me, they are all one system which allows coordination of the activities of cells in the body.

Anxiety is a sign of excessive norepinephrine signaling – a sign that the sympathetic nervous system – a component of the nervous system is overactive. Excessive norepinephrine signaling has multiple possible causes – including hypothyroidism, hypothalamic-pituitary-adrenai dysfunction, iron deficiency, serotonin deficiency, excessive life stresses, etc. etc.

The nervous system has direct neuron connections to the lymph notes and the gastrointestinal system. The gastrointestinal system has the largest concentration of white blood cells and other cells of the immune system of any system.

Increase norepinephrine/stress signaling can then cause direct stimulation via norepinephrine release from the end of sympathetic nervous system axons to the cells of the immune system, causing activation of the immune system. The immune system cells then start releasing pro-inflammatory cytokines.

Increased norepinephrine signaling can active the brain’s microglia, which then produce inflammatory cytokines – such as IL-6. This then activates the immune system cells, causing them to release pro-inflammatory cytokines.

Increase stress/norepinephrine signaling can also active that brain’s mast cells, causing a release of histamine. The release of histamine can then also activate the immune system’s cells.

The activation of the immune system’s cells and the release of histamine and pro-inflammatory cytokines trigger inflammation.

Inflammation is a sign of an activated immune system.

When an infection occurs, the immune system’s cells are again activated by their mast cells and macrophages which sense a foreign invasion. The immune system cells at the sign of infection then start releasing large amounts of pro-inflammatory signals to activate immune system activity. These pro-inflammatory signals enter the brain causing a stress response, which can then active the sympathetic nervous system. This may then result in anxiety depending on a number of factors.

This is just a brief description of highly complex interactions involving information processing and response to stress between the systems.