Calm on the Outside, Chaos on the Inside: Autism, ADHD, the Vagus Nerve, and the Hidden Physical Cost of Overwhelm
Why so many neurodivergent people seem to experience overlapping physical symptoms and what we can actually do about it.
Have you ever noticed how certain health complaints seem to travel in packs?
Someone has ADHD or autism, and somewhere along the way you discover they also experience chronic muscle tension, jaw clenching, migraines, digestive problems, dizziness when standing, unusual fatigue, or some combination of seemingly unrelated symptoms.
Sometimes there are diagnoses like postural orthostatic tachycardia syndrome (POTS), irritable bowel syndrome (IBS), hypermobile Ehlers-Danlos syndrome (hEDS), or an autoimmune condition in the mix.
And sometimes there are no additional diagnoses. Just a person who feels as though their body has been bracing for impact since approximately 1997.
As a therapist who works with neurodivergent people, I've become increasingly interested in these patterns.
I hear about shoulders that never relax, jaws that remain clenched, digestive systems that seem to have their own unpredictable agendas, and bodies that swing between feeling wired and completely exhausted.
The question that keeps coming back to me is:
What if some of the physical difficulties experienced by neurodivergent people are connected—not necessarily by one underlying disease, but through overlapping biological vulnerabilities, autonomic regulation, and the cumulative demands of navigating the world?
There's a growing body of research suggesting this question deserves serious attention.
But before we start blaming everything on the vagus nerve, let's look at what we know, what we suspect, and what remains uncertain.
Your Autonomic Nervous System: The Background Processes
Your autonomic nervous system (ANS) manages many functions that normally happen without conscious direction. Heart rate. Blood pressure regulation. Digestion. Sweating. Changes in blood vessel diameter. Many aspects of physiological arousal and recovery. It's a little like the background software running your body while you're busy doing other things.
The sympathetic nervous system helps mobilize resources during challenges. The parasympathetic nervous system supports functions that include digestion and aspects of physiological recovery. The vagus nerve is a major part of the parasympathetic system, communicating between the brain and organs including the heart and digestive tract.
These systems don't operate as simple opposing switches. They're continuously adjusting to what the body needs. Which brings us to a frequently ignored but very important point:
Your nervous system responds to demands whether or not you consciously identify those demands as stressful.
A crowded grocery store might not seem particularly threatening. But what if your brain is simultaneously managing fluorescent lighting, competing conversations, movement, unfamiliar people, decision-making, smells, temperature, and the executive-function challenge of remembering why you came?
That's a lot of processing and it is all happening while you're smiling politely and appearing perfectly fine.
The Difference Between Looking Regulated and Being Regulated
This is where masking becomes particularly interesting. Masking, or camouflaging, refers to strategies some autistic people use to conceal, compensate for, or modify characteristics that might attract unwanted attention. It can include consciously monitoring facial expressions, suppressing repetitive movements, rehearsing conversations, forcing eye contact, or hiding sensory discomfort.
Masking isn't automatically bad.
We all modify our behavior in different environments. Social adaptation is a useful human skill. The concern is what happens when someone must maintain an exhausting level of self-monitoring for hours every day, particularly when doing so requires ignoring internal signals of discomfort or distress.
Imagine you're attending a meeting. You're making eye contact, monitoring your facial expression, remembering not to interrupt, interpreting social cues, managing background noise, trying to sit still, and following the conversation. Meanwhile, your body may be telling you:
Too much. Too loud. Need to move. Need a break.
But the meeting continues. And you continue performing. You look calm, maybe even confident. But physiologically?
Masking and biological stress
A particularly interesting study published in 2025 examined camouflaging and stress in 315 twins, including 69 diagnosed autistic participants. Researchers found an association between camouflaging and higher hair cortisol concentrations, a marker used to study longer-term stress exposure. The association was particularly evident in autistic and adult subgroups.
This is of note because it goes beyond asking people whether masking feels stressful. It examines a biological indicator. However, it doesn't establish that masking causes elevated cortisol or that cortisol explains the physical conditions discussed in this article. We need more research.
Looking comfortable and experiencing low physiological stress are not necessarily the same thing.
The Body Keeps Responding Even When We Keep Performing
Chronic stress involves more than simply feeling worried. Over time, repeated or sustained physiological demands can affect sleep, muscle tension, digestion, pain sensitivity, immune signaling, and other bodily processes. Researchers sometimes use the concept of allostatic load to describe the cumulative physiological burden associated with adapting to repeated or chronic stressors.
This doesn't mean every stress response is harmful. Stress responses are necessary for survival. The concern is the combination of repeated demands, inadequate recovery, and individual vulnerability. For neurodivergent people, those demands may include more than conventional life stress.
There may also be sensory overload, executive-function demands, social monitoring, disrupted sleep, chronic pain, unpredictable environments, and the effort of functioning in systems that don't fit their needs particularly well. That makes the relationship between neurodivergence and chronic physiological stress worth investigating.
It would be a mistake to assume stress is the sole explanation for every physical symptom. Some of these conditions have biological mechanisms that require medical assessment and treatment regardless of stress levels.
Why Do These Symptoms Seem to Travel Together?
Let's look at several of the patterns that have attracted researchers' attention.
1. Chronic Muscle Tension, Jaw Clenching, and Headaches
Many people describe living with muscles that never seem to fully relax. Shoulders up around their ears. Tension at the base of the skull. A tight jaw. Headaches. Teeth grinding.
The research on bruxism—clenching or grinding the teeth—is particularly interesting. A 2022 systematic review and meta-analysis found higher observed odds of bruxism in autistic participants compared with controls. However, the authors rated the certainty of evidence as very low. A September 2026 systematic review involving more than 16,000 participants also found an association between ADHD and bruxism, with approximately twice the odds compared with people without ADHD.
Neither finding proves that autonomic dysregulation is the cause. Still, it gives us a concrete example of a physical symptom worth taking seriously rather than automatically dismissing as anxiety.
2. Digestive Problems
The digestive system and nervous system communicate constantly. The vagus nerve participates in that communication, although it is far from the only pathway involved. Autistic people frequently report gastrointestinal symptoms, and GI complaints are also common among people with ADHD. Possible contributors include differences in eating patterns, food selectivity, sensory sensitivities, medication effects, gut motility, sleep, stress, and co-occurring medical conditions.
3. POTS and Blood Pressure Regulation
POTS is a disorder involving abnormal heart-rate responses to upright posture, usually accompanied by symptoms such as dizziness, palpitations, fatigue, and exercise intolerance. It belongs to a broader family of conditions involving autonomic dysfunction.
POTS is not simply anxiety, although its symptoms can resemble anxiety and the conditions can coexist. Autonomic problems may involve multiple physiological mechanisms, including blood volume, vascular regulation, neuropathic processes, and other factors. Some researchers are investigating connections between neurodevelopmental conditions, autonomic dysfunction, and joint hypermobility.
The existence of overlapping diagnoses does not mean one causes another. It also doesn't mean that vagus nerve stimulation is an established treatment for POTS.
4. Hypermobility and Connective Tissue Differences
This may be one of the most intriguing parts of the larger picture. A 2025 systematic review and meta-analysis examined autism in relation to joint hypermobility, hypermobility spectrum disorders, and Ehlers-Danlos syndromes. The researchers found evidence of associations between autism and hypermobility-related conditions.
Why does this matter? Because connective tissue influences much more than joint flexibility. Hypermobility-related disorders can coexist with pain, fatigue, gastrointestinal symptoms, and orthostatic intolerance. That creates a possible route through which some apparently unrelated physical symptoms may cluster.
It also reminds us that not every symptom needs to be explained by stress. Sometimes the nervous system and the body's structural systems are both contributing to the problem.
5. Immune and Autoimmune Conditions
This is an area where we need to be especially careful because it is related to some of the most toxic misinformation out there. There is research examining immune differences and associations between neurodevelopmental conditions and some immune-mediated diseases. But autoimmune diseases are not all the same thing.
Chronic stress can influence immune functioning; that doesn't establish that masking causes autoimmune disease. Some people have several conditions simultaneously, but determining whether they share mechanisms, or simply overlap more often than expected, requires careful research.
Could Autonomic Regulation Be Part of the Common Thread?
Possibly.
Research using heart rate variability (HRV) and respiratory sinus arrhythmia (RSA) has identified group-level differences in aspects of autonomic regulation among autistic and ADHD populations. These measures can provide indirect information about cardiac parasympathetic regulation.
Some studies suggest differences in resting activity, physiological reactivity, or recovery from demands. However, results vary substantially. Not every autistic or ADHD person has low HRV. HRV is influenced by age, breathing, fitness, sleep, medication, health conditions, and measurement methods. HRV does not measure someone's entire nervous system, nor can it tell us whether a person is masking or approaching burnout.
Still, the broader research supports investigating how physiological regulation interacts with cognitive demands, sensory processing, emotion, and recovery. I suspect that understanding those interactions could help us develop more useful strategies for preventing overwhelm.
But that is a research direction, not a conclusion that has already been demonstrated.
The Vagus Nerve: An Interesting Therapeutic Target
This brings us to a rapidly growing area of interest: vagus nerve stimulation.
Vagus nerve stimulation, or VNS, uses electrical stimulation to influence neural pathways involving the vagus nerve. There are several different approaches.
Implanted VNS devices have established medical uses for certain conditions, including treatment-resistant epilepsy and depression in selected patients.
Noninvasive approaches, including transcutaneous auricular vagus nerve stimulation (taVNS), use electrodes placed on particular areas of the outer ear. These devices are being studied for a variety of neurological and psychiatric conditions and are available to the general public without a prescription.
The attraction is understandable. If autonomic regulation contributes to some symptoms, perhaps modifying activity in these pathways could help.
But there are two very important distinctions.
First, stimulating the vagus nerve is not the same thing as treating every condition associated with autonomic dysfunction.
Second, a consumer device advertised as a vagus nerve stimulator is not automatically equivalent to a device used in a controlled clinical trial.
What Does the Research Say About Vagus Nerve Stimulation?
There is growing interest in noninvasive VNS, including research relevant to attention, mood, stress regulation, and neurodevelopmental conditions. The evidence for using home vagal stimulation devices specifically to prevent autistic or ADHD overwhelm remains preliminary. There is a growing body of anecdotal evidence that indicates this approach may be useful.
A systematic review of transcutaneous auricular VNS safety found that reported adverse events were generally mild, commonly including ear pain, headache, and tingling. For people with significant autonomic or cardiovascular symptoms, medical guidance is especially important before experimenting with electrical stimulation devices.
What Can We Do Right Now?
Fortunately, we don't have to wait for every biological mechanism to be identified before helping people manage overwhelm. And we don't necessarily need an expensive device. I think the most productive approach is to focus on improving the fit between a person's nervous system, daily demands, and opportunities for recovery.
1. Recognize Your Early Warning Signs
Overwhelm doesn't always arrive suddenly.
For some people, early signs include:
Increased jaw clenching.
Shoulder or neck tension.
Shallow or rapid breathing.
Difficulty concentrating.
Increased irritability.
Sensory sensitivity.
Digestive discomfort.
An urge to withdraw.
Trouble finding words.
Reduced tolerance for ordinary demands.
The goal is to recognize patterns before reaching the point of complete overload.
These signs are not specific to autism or ADHD, and new or worsening symptoms deserve appropriate medical evaluation.
2. Reduce the Load Before Trying to Increase Your Tolerance
Sometimes the most effective regulation strategy isn't teaching yourself to tolerate more. It's reducing unnecessary demands. Wear the headphones. Change the lighting. Take the break. Create a quieter workspace. Use written instructions. Stop multitasking. Plan recovery time after demanding activities and actually observe them
A nervous system that is already managing substantial demands may benefit more from fewer demands than from another technique designed to push through them.
3. Experiment With Gentle Regulation Strategies
Depending on the individual, helpful strategies might include comfortable, unforced breathing, progressive muscle relaxation, movement, mindfulness, or sensory adjustments. No single technique works for everyone.
Slow breathing can be calming for some people and uncomfortable for others.
Body-focused exercises can be distressing for people with certain trauma histories or interoceptive sensitivities.
People with POTS or other medical conditions may need modifications to movement and breathing practices.
The goal is not to force the body into an idealized state of calm. It's to find strategies that actually improve functioning.
4. Address the Physical Symptoms Directly
If you're grinding your teeth, talk with a dental professional.
If you're experiencing dizziness or rapid heart rate when standing, seek evaluation for orthostatic intolerance.
If digestive symptoms are persistent, investigate them.
If you have chronic pain or unusual joint flexibility, ask whether assessment for hypermobility-related conditions is appropriate.
If you're experiencing symptoms suggestive of autoimmune disease, discuss them with a medical professional.
Stress management may help some symptoms.
It should never become an excuse to overlook treatable medical conditions.
5. Build Recovery Into Your Routine
One of the biggest challenges I see is people waiting until they're completely depleted before allowing themselves to rest. They function all day. They manage their sensory environment. They perform socially. They meet expectations and push through discomfort. Then they collapse at home.
Sometimes recovery needs to become a planned part of functioning rather than a last resort after functioning fails. Think of it as resource management. If you know a particular encounter drains your mana bar, you don't wait until you're completely empty before considering how you're going to recover.
6. Track What Actually Helps
This is where a little self-experimentation can be useful.
Notice patterns in your sleep, sensory exposure, social demands, pain, digestive symptoms, muscle tension, energy, and recovery. You don't need to monitor every bodily sensation obsessively. In fact, excessive monitoring can sometimes increase anxiety. But a simple record may reveal patterns.
Perhaps jaw tension increases after prolonged meetings. Perhaps digestive symptoms worsen after poor sleep. Perhaps social interactions are much easier when you have quiet recovery time afterward.
These observations don't prove causation but they can help you identify practical changes worth trying.
We Need to Stop Confusing Endurance With Regulation
Many neurodivergent adults become extraordinarily skilled at enduring discomfort. They learn to keep working while overwhelmed. They learn to socialize while exhausted. They learn to ignore sensory distress. They learn to appear calm when their bodies are demanding relief. And because they can continue performing, people assume they're fine.
Sometimes they assume they're fine themselves.
Until they aren't.
The ability to endure a demand is not the same thing as the ability to recover from it.
And appearing capable doesn't mean the effort is free.
I think we need to become much more interested in what functioning costs a person, not simply whether they can produce the expected behavior. This is especially important for adults whose support needs are underestimated because they speak fluently, work, maintain relationships, or otherwise appear outwardly successful.
A Different Way to Think About Self-Regulation
What if self-regulation isn't simply the ability to suppress visible distress?
What if it also includes: Recognizing internal signals. Understanding our physiological needs. Modifying our environments. Choosing appropriate supports. Managing demands. Allowing recovery. And knowing when something requires medical attention rather than another coping skill?
That is a much broader and, I would argue, more useful understanding of regulation. It doesn't ask people to become less neurodivergent. It asks how we can help them function with less unnecessary distress.
The Research Is Still Catching Up
I don't believe we currently have enough evidence to say that the vagus nerve explains the entire cluster of symptoms many neurodivergent people report. That would be too simple.
Autonomic regulation, connective tissue, immune functioning, gastrointestinal physiology, sleep, pain, medications, genetics, stress, and environmental demands may all contribute in different ways. Some relationships are well documented. Some are emerging. Some are totally hypothetical.
My hope is that research will eventually help us identify which interventions are most useful for which people. Perhaps vagus nerve stimulation will become one valuable tool for certain individuals. Perhaps better understanding of autonomic regulation will lead to improved treatments for specific symptoms.
I think perhaps one of the biggest improvements will come from something much less technologically exciting:
Learning to recognize nervous system overwhelm earlier and creating lives that don't require people to remain overwhelmed in order to be considered successful.
Because the goal isn't to become better at pretending we're fine it is to actually feel better.
Educational note: This article discusses associations and emerging research, not established causal explanations. Autism and ADHD are heterogeneous neurodevelopmental conditions, and the physical symptoms described here can have many causes. Vagus nerve stimulation is not an established general treatment for autistic or ADHD overwhelm. Persistent, new, or worsening physical symptoms deserve appropriate medical assessment.