Anxiety is often described as a mental or emotional problem—something caused by stress, trauma, or thought patterns. Sometimes that’s true. But for many people, especially those living with chronic illness, anxiety doesn’t begin in the mind at all. It begins in the immune system.
In these cases, anxiety isn’t a character flaw or a failure to cope. It’s a physiologic response—the brain reacting to signals that the body is under strain.
The brain’s alarm system responds to the body
Deep within the brain is a structure called the amygdala, whose job is to scan for danger and help keep us safe. When a real threat appears, this system works beautifully, increasing alertness and readiness to respond.
But the amygdala doesn’t just respond to the outside world. It also listens closely to internal signals from the body.
When the immune system is activated—by infection, chronic inflammation, autoimmune activity, toxin exposure, or prolonged physiologic stress—it releases chemical messengers called cytokines. These signals help coordinate immune defense, but they also communicate directly with the brain. Over time, persistent immune signaling can cause the amygdala to become hyper-reactive, like a smoke alarm that goes off even when there’s no fire.
When this happens, anxiety and panic can feel sudden, intense, and out of proportion—or appear without any obvious trigger.
Why anxiety often feels physical, not psychological
Many people with immune-driven anxiety describe experiences like:
- “My thoughts are calm, but my body feels panicked.”
- “I don’t feel stressed, but my heart races and my chest tightens.”
- “I wake up anxious without knowing why.”
This happens because inflammation lowers the brain’s threshold for detecting threat. Research shows that immune signals can increase activity in fear-processing regions of the brain, particularly the amygdala. When the nervous system is constantly receiving danger signals from the body, it stays on high alert—even in safe situations.
This helps explain why anxiety so often accompanies chronic infections, autoimmune conditions, long-COVID–type patterns, mold or toxin exposure, and other inflammatory illnesses—and why reassurance alone rarely resolves it.
The immune system and anxiety reinforce each other
This relationship is a two-way street.
Immune activation can trigger anxiety.
And chronic anxiety activates stress hormones like cortisol that, over time, can disrupt immune regulation.
The result is a feedback loop:
- inflammation heightens anxiety
- anxiety increases physiologic stress
- stress weakens immune balance
- inflammation persists
Over time, this cycle can affect not only mood, but also energy, focus, sleep, and resilience, often showing up as fatigue or brain fog alongside anxiety.
Why the old explanations fall short
For decades, anxiety has been explained mainly as a neurotransmitter problem—too little serotonin, not enough GABA, imbalance in dopamine. While these chemicals matter, that theory was never definitively proven to explain most anxiety disorders. It also doesn’t account for why anxiety fluctuates with illness, inflammation, infection, or immune stress.
What newer science shows is that immune signaling sits upstream of neurotransmitters. Inflammation can change how brain circuits fire and how safe or unsafe the world feels—before conscious thoughts even come into play.
This is one reason the historical separation between psychiatry and neurology no longer makes sense.
Brain health is mental health.
And the immune system is deeply involved in both.
When to suspect anxiety has an immune component
An immune-driven pattern is more likely when anxiety:
- appears suddenly or later in life
- doesn’t respond well to standard treatments
- worsens during illness or inflammatory flares
- is accompanied by fatigue, pain, or flu-like symptoms
- tracks physical health more than life circumstances
In these cases, anxiety isn’t the root problem. It’s a signal.
A clearer, more hopeful way to understand anxiety
Seen this way, anxiety isn’t a label to live with forever. It’s a signal—one that tells us the body and brain have been under more strain than they can comfortably manage. When anxiety shows up suddenly, doesn’t respond well to usual treatments, or rises and falls with physical health, it often points to deeper root cause issues affecting immune function.
As those upstream drivers are identified and addressed within the Root Cause Triad, the system begins to settle. In many cases, anxiety eases or fades away—not because it was forced down, but because the body no longer needs to stay on constant alert.