When the Body Sounds the Alarm: Autonomic Dysregulation, Physical Anxiety Symptoms, and Medically Unexplained Symptoms
Have you ever experienced a racing heart, dizziness, nausea, chest tightness, trembling, shortness of breath, or a feeling that something is seriously wrong with your body—only to have medical testing come back normal?
These experiences can be confusing and frightening. You may know that you feel physically unwell, while simultaneously being told that “nothing is wrong.”
The reality is more nuanced.
Our physical symptoms are real, even when conventional medical testing does not identify a clear structural cause. One way of understanding these experiences is through the autonomic nervous system (ANS) and the concept of autonomic dysregulation.
Understanding how the nervous system influences the body can help explain why anxiety can feel so physical—and why physical symptoms can sometimes persist even when no clear medical explanation is found.
What is the autonomic nervous system?
The autonomic nervous system is part of the nervous system responsible for regulating many functions that happen automatically, without conscious effort.
It helps coordinate things such as:
Heart rate
Blood pressure
Breathing
Digestion
Body temperature
Sweating
Muscle tension
Pupil dilation
Energy and alertness
The autonomic nervous system is constantly adjusting your body's internal state in response to what is happening around you and within you. When you perceive safety, your body can generally support rest, digestion, connection, and recovery. When your brain detects threat, the autonomic nervous system can shift the body toward protection.
This is useful when there is an immediate danger. The difficulty arises when the body's threat-response system becomes overly sensitive, remains activated for prolonged periods, or has difficulty returning to a regulated state.
Anxiety isn't only an emotion—it is a physical state
Anxiety is often described as a psychological experience involving worry, fear, or apprehension. However, anxiety also involves significant physiological changes. When the brain perceives a threat, it can activate the body's defensive systems. This may result in:
Increased heart rate
Faster or shallower breathing
Muscle tension
Sweating
Shaking or trembling
Changes in digestion
Nausea or abdominal discomfort
Dizziness or lightheadedness
Tingling or altered sensations
Feeling hot or cold
Increased alertness
Difficulty concentrating
These sensations can themselves become frightening and overwhelming.
For example, someone may notice their heart suddenly beating quickly. They may interpret this as evidence that something is wrong with their heart. That interpretation increases fear, which can further activate the nervous system, producing even more physical sensations.
A cycle can develop:
Physical sensation → threat interpretation → increased anxiety → increased autonomic activation → stronger physical sensation
This does not mean the symptoms are imagined. It means that the nervous system and the body are communicating continuously.
What is autonomic dysregulation?
Autonomic dysregulation is a broad term used to describe difficulties with the regulation of autonomic nervous system activity.
The autonomic nervous system is not simply an “on or off” system. It continually adjusts according to internal and external demands.
Sometimes, following prolonged stress, illness, trauma, pain, sleep disruption, or other physiological challenges, the nervous system may become more reactive or less flexible. A person may find that their body responds intensely to relatively small triggers.
When symptoms don't have a clear medical explanation
Some people experience persistent physical symptoms that cannot be fully explained by the medical tests or investigations they have received. Historically, these symptoms have sometimes been described as “medically unexplained.” Unfortunately, this phrase can feel dismissive. If you are experiencing pain, dizziness, weakness, fatigue, gastrointestinal symptoms, sensory changes, or other physical symptoms, the absence of an identifiable disease does not mean that you are imagining them.
Medicine continues to develop its understanding of how the nervous system, brain, immune system, hormones, emotions, behaviour, and environment interact. In some cases, symptoms may be associated with changes in nervous-system functioning rather than identifiable structural damage.
Why symptoms can continue after the original trigger is gone
One of the most confusing aspects of nervous-system-related symptoms is that they can persist even after the original stressor has passed.
Imagine a smoke alarm that has become highly sensitive. The alarm is not “fake.” It is performing its job. However, it may begin responding to stimuli that do not represent an actual fire.
Similarly, a nervous system that has become highly sensitized may respond strongly to sensations, environments, thoughts, or bodily changes that are not inherently dangerous. This does not mean that the nervous system is broken. Rather, the system may have learned to respond protectively. And psychotherapy tries to change this pattern.
The role of stress and trauma
Chronic stress and experiences of trauma can influence how the nervous system responds to perceived threat. This does not mean that every unexplained physical symptom is caused by trauma. There are many possible contributors to physical symptoms, including medical conditions, medications, sleep, hormonal factors, neurological conditions, pain, illness, environmental factors, and psychological stress.
However, for some people, prolonged stress may contribute to increased physiological arousal or difficulty returning to a calmer state following activation. The body may essentially become accustomed to operating in a state of heightened readiness. This can look different from person to person - one person may experience anxiety primarily through their heart and breathing. Another may experience gastrointestinal symptoms, headaches, muscle tension, fatigue, dizziness, or sensory changes.
Why reassurance doesn't always make symptoms disappear
If your symptoms are being influenced by autonomic activation, being told “your tests are normal” may provide temporary reassurance but may not completely resolve the physical experience. This is because knowing intellectually that you are safe and feeling safe in your body are not always the same thing.
Someone might think:
“I know my doctor said my heart is okay, but my heart is still racing.”
The body may continue responding even when the conscious mind understands that there is no immediate danger. This is one reason that approaches focused on the nervous system and the body can sometimes complement traditional medical care.
A somatic approach
Somatic psychotherapy focuses on developing greater awareness of the relationship between physical sensations, emotions, thoughts, behaviours, and the environment.
Rather than immediately trying to eliminate a sensation, therapy may involve learning to notice what is happening in the body with curiosity and without automatically interpreting the sensation as dangerous.
For example:
Notice:
“My chest feels tight.”
Explore:
“What happens when I bring gentle attention to that sensation?”
Orient:
“Is there anything around me that signals safety right now?”
Differentiate:
“Is this sensation changing, staying the same, or becoming stronger?”
Regulate:
“What helps my body move toward greater steadiness?”
The goal is not to convince yourself that symptoms are imaginary.
The goal is to develop a different relationship with the sensations your body is producing.
You don't have to choose between “physical” and “psychological”
Perhaps one of the most important things to understand is that physical and psychological explanations are not necessarily competing explanations.
A symptom can be physically experienced and influenced by the nervous system. Anxiety can produce genuine physiological changes. Stress can affect digestion, breathing, muscle tension, heart rate, sleep, pain sensitivity, and many other bodily processes. And pre-existing medical conditions can also influence emotional wellbeing and nervous-system functioning.
Your symptoms deserve to be taken seriously
If you are experiencing new, severe, worsening, or unexplained physical symptoms, it is important to seek appropriate medical assessment. Nervous-system regulation should not be used as a substitute for ruling out medical conditions when indicated. At the same time, receiving normal test results does not mean that your experience is “all in your head.”
There is a middle ground between identifying a structural medical disease and dismissing symptoms as imaginary. The nervous system provides one important framework for understanding that middle ground. When we begin to understand symptoms as communication from a complex mind-body system, the question can shift from:
“Why can't anyone find what's wrong with me?”
to:
“What might my nervous system be responding to, and what could help my body feel safer and more regulated?”
That shift can open up new possibilities for understanding and supporting the body—while continuing to respect the importance of appropriate medical care.