When It's Not 'Just Anxiety': How MCAS, POTS, and EDS Can Be Mistaken for Mental Illness

Have you ever been told your symptoms are "all in your head"? If you experience a combination of anxiety, brain fog, dizziness, racing heart, stomach problems, flushing, and fatigue — and your doctors can't seem to find a single explanation — you are not alone, and you are not imagining things.

A growing body of medical research is revealing that three interconnected physical conditions are frequently misdiagnosed as anxiety, panic disorder, depression, or "somatic symptom disorder" (the modern term for what used to be called psychosomatic illness). These conditions are Mast Cell Activation Syndrome (MCAS), Postural Orthostatic Tachycardia Syndrome (POTS), and Ehlers-Danlos Syndrome (EDS). This post explains what these conditions are, how they overlap with mental health symptoms, and what you can do if you think you might be affected.

What Are MCAS, POTS, and EDS?

Mast Cell Activation Syndrome (MCAS) is a condition in which mast cells — immune cells found throughout the body — release too many chemical signals (including histamine) at inappropriate times. This can cause episodes of flushing, hives, itching, stomach cramps, diarrhea, wheezing, brain fog, and even anxiety or panic-like symptoms. These episodes are often triggered by heat, stress, certain foods, hormonal changes, or physical activity.

Postural Orthostatic Tachycardia Syndrome (POTS) is a disorder of the autonomic nervous system — the system that controls heart rate, blood pressure, digestion, and other automatic body functions. When people with POTS stand up, their heart rate increases excessively (30 or more beats per minute), causing lightheadedness, dizziness, palpitations, brain fog, and sometimes fainting. These symptoms are often mistaken for anxiety or panic attacks.

Ehlers-Danlos Syndrome (EDS), particularly the hypermobile type (hEDS), is a connective tissue disorder that causes overly flexible joints, chronic pain, easy bruising, and fatigue. Because connective tissue is found everywhere in the body, EDS can affect the skin, gut, heart, and nervous system.

These three conditions frequently occur together. Research shows that in patients who have both POTS and EDS, the odds of also having MCAS are more than 30 times higher than in the general population.

Why These Conditions Get Mistaken for Mental Illness

The symptoms of MCAS, POTS, and EDS overlap dramatically with common psychiatric diagnoses:

- A racing heart and lightheadedness upon standing (POTS) looks like a panic attack

- Episodic flushing, stomach distress, and a sense of impending doom during a mast cell flare (MCAS) mimics generalized anxiety

- Chronic fatigue, brain fog, and difficulty concentrating (all three conditions) resemble depression

- Widespread pain that moves around the body (EDS/MCAS) can be labeled somatic symptom disorder

Because these conditions affect multiple body systems at once, patients often see many different specialists — a cardiologist for the racing heart, a gastroenterologist for the stomach problems, a neurologist for the brain fog — and each specialist may find nothing wrong in their specific area. When no single specialist can explain the full picture, patients are frequently referred to psychiatry with a label of "somatoform disorder" or "conversion disorder," meaning their doctors believe the symptoms are caused by psychological distress rather than a physical illness.

The numbers are sobering. In the largest survey of POTS patients (nearly 5,000 people), the average time to diagnosis was two years, and most patients received incorrect diagnoses first. In a study of children with POTS, more than half were told their symptoms were "in their head." A multinational physician audit found that approximately 80% of POTS patients received wrong diagnoses before the correct one was made.

The Science: Why These Conditions Cause "Psychiatric" Symptoms

The psychiatric symptoms in MCAS, POTS, and EDS are not imaginary — they have clear biological explanations.

Histamine is both an immune molecule and a brain chemical. When mast cells release too much histamine (as in MCAS), it doesn't just cause hives and stomach problems. Histamine is also a neurotransmitter — a chemical messenger in the brain. It regulates wakefulness, anxiety, and mood. Excess histamine in the brain can directly cause insomnia, anxiety, and agitation.

Inflammation disrupts brain chemistry. When mast cells are overactive, they release inflammatory chemicals that can cross into the brain and interfere with the production of serotonin — the brain chemical most commonly targeted by antidepressants. Specifically, inflammation activates an enzyme that diverts the building blocks of serotonin toward toxic byproducts instead. Research in patients with mast cell disease has confirmed that their serotonin levels are lower and their toxic byproduct levels are higher — and that these changes directly correlate with depression severity.

The vagus nerve connects the body to the brain. The vagus nerve is the longest nerve in the body, running from the brainstem to the gut, heart, and other organs. It acts as a communication highway between the body and brain. When the vagus nerve isn't functioning properly — as can happen in POTS and other autonomic disorders — the brain loses its ability to properly regulate inflammation, mood, and stress responses. This creates a vicious cycle: body inflammation worsens brain function, and impaired brain regulation worsens body inflammation.

Mast cells sit right next to nerves. Mast cells are physically located next to nerve endings throughout the body — including in the brain, heart, and gut. This means that when mast cells release their chemicals, they directly affect nerve function. This anatomic relationship explains why POTS, MCAS, and neuropsychiatric symptoms so often occur together.

What You Can Do: Advocating for Yourself

If you recognize yourself in this description, here are concrete steps you can take:

1. Track your symptoms across body systems. Keep a daily log that includes not just your mood and anxiety levels, but also your heart rate (especially when standing), any flushing or skin changes, stomach symptoms, joint pain, and brain fog. Note what triggers episodes — heat, stress, certain foods, menstrual cycle changes, exercise. The pattern of symptoms affecting multiple body systems and occurring in episodes is the key clue that distinguishes these conditions from primary anxiety or depression.

2. Ask for a simple standing heart rate test. POTS can be screened for in any doctor's office with just a blood pressure cuff. The test involves lying down for 5 minutes, then standing quietly for 10 minutes while your heart rate and blood pressure are checked at regular intervals. If your heart rate increases by 30 or more beats per minute and stays elevated — and you feel symptomatic — that is a positive screen for POTS. You do not need a tilt table test for an initial diagnosis.

3. Ask about a trial of antihistamines. If MCAS is suspected, a trial of over-the-counter antihistamines — a nonsedating antihistamine like cetirizine (Zyrtec) plus an acid-reducing antihistamine like famotidine (Pepcid) — is safe, inexpensive, and can be very informative. If your "anxiety," brain fog, and stomach symptoms improve significantly on antihistamines, that strongly suggests a mast cell component rather than a primary psychiatric disorder. Discuss this with your provider before starting.

4. Ask about joint hypermobility. A simple physical exam called the Beighton score can screen for the joint hypermobility seen in EDS. It takes about two minutes and requires no special equipment. If you've always been "double-jointed," experience frequent joint pain or subluxations, bruise easily, or have stretchy skin, mention this to your provider.

5. Know what to say to your providers. If you have been labeled with "somatic symptom disorder" or told your symptoms are psychological, you can respectfully ask: "Have POTS, MCAS, and [hypermobile EDS](/rare-disease/hypermobile-ehlers-danlos-syndrome) been specifically evaluated and ruled out?" These are recognized medical conditions with established diagnostic criteria, and they require specific testing that is different from routine bloodwork.

6. Request appropriate referrals. If screening suggests one or more of these conditions, the appropriate specialists include:

- A cardiologist or neurologist with autonomic expertise (for POTS)

- An allergist-immunologist (for MCAS)

- A geneticist or rheumatologist familiar with connective tissue disorders (for EDS)

A Note About Mental Health

Having MCAS, POTS, or EDS does not mean you cannot also have a mental health condition. Many people with these conditions do experience genuine anxiety, depression, or PTSD — sometimes as a direct biological consequence of their disease, and sometimes as a natural emotional response to years of being undiagnosed, dismissed, or disbelieved.

The important distinction is this: if your psychiatric symptoms are being driven by an underlying physical condition, treating only the psychiatric symptoms (with antidepressants or therapy alone) may not be enough. Addressing the root cause — the mast cell activation, the autonomic dysfunction, the connective tissue disorder — can sometimes improve or even resolve the "psychiatric" symptoms.

The best outcomes happen when mental health providers and medical specialists work together, each recognizing their piece of the puzzle.

The Bottom Line

If you have been struggling with a combination of anxiety, brain fog, racing heart, dizziness, stomach problems, flushing, chronic pain, and fatigue — and you've been told it's "just anxiety" or "all in your head" — it may be worth exploring whether MCAS, POTS, or EDS could be contributing. These are real, diagnosable, treatable conditions. Getting the right diagnosis can be life-changing.

You deserve to be heard, believed, and properly evaluated.

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