Is There a Link Between MCAS and Neurodivergence? What the Research Is Starting to Show
For the autistic or ADHD adult who has always felt like their body was fighting something no one could name
If you are autistic or have ADHD and you have also spent years dealing with unexplained physical symptoms — chronic fatigue, gastrointestinal issues, food sensitivities, skin reactions, brain fog that no one could explain, sensory overwhelm that seemed far more intense than it “should” be — you are not imagining it. And you are not alone. There is emerging research suggesting that your immune system and your nervous system may be doing something very similar, and that the connection between Mast Cell Activation Syndrome and neurodivergence is real, biologically grounded, and profoundly underrecognized.
As a neurodivergent-affirming clinician I want to be clear about something from the outset: this blog is not a diagnostic tool. I am a licensed clinical social worker, not a physician or immunologist. What I am offering here is a synthesis of emerging research that I believe every autistic and ADHD adult deserves to know exists — because for many people in my community, this information has been life-changing. If you recognize yourself in what follows, the next step is a conversation with a physician who understands the intersection of immune dysfunction and neurodivergence.
What Is Mast Cell Activation Syndrome?
Mast Cell Activation Syndrome — MCAS — is an immunological condition in which mast cells, a type of white blood cell, inappropriately and excessively release chemical mediators including histamine, leading to a range of chronic, multi-system symptoms. Mast cells are found throughout the body — in the gut, skin, lungs, and crucially, in the brain — and when they malfunction, the effects can touch virtually every body system simultaneously.
Primary symptoms of MCAS include cardiovascular irregularities, gastrointestinal distress, skin reactions, respiratory problems, and neurological symptoms. Because MCAS affects so many systems at once and its symptoms fluctuate and overlap with dozens of other conditions, it is frequently missed, dismissed, or misdiagnosed — sometimes for decades.
“Mast cells are found throughout the body — including in the brain. When they malfunction, the effects can touch virtually every body system simultaneously. For neurodivergent people, who are already navigating a world that doesn’t fit their nervous system, MCAS can be the invisible layer underneath everything.”
What the Research Is Finding
The connection between MCAS and neurodivergence is not a social media theory. It is an emerging area of legitimate scientific inquiry with peer-reviewed research building steadily behind it. Here is what the studies are currently showing:
Research Finding 1 — MCAS and Autism: Overlapping Symptom Profiles
A 2025 review published in ScienceDirect examined the role of mast cells in Autism Spectrum Disorder. The researchers found that mast cell mediators including histamine, serotonin, and cytokines influence neuroinflammatory pathways that are altered in ASD, and that increased mast cell activity may be linked to the development of autism in certain individuals.
Source: ScienceDirect, “The role of mast cells in Autism Spectrum Disorder” (June 2025)
Research Finding 2 — Shared Symptom Overlap: Sensory, GI, and Cognitive
Research has found that the symptom profiles of MCAS and autism overlap significantly — including gastrointestinal disturbances, sensory hypersensitivities, sleep irregularities, neuroinflammation, and cognitive impairment. This overlap is not coincidental. It points to shared biological mechanisms involving immune dysregulation and histamine activity in the nervous system.
Source: Theoharides, T.C., et al. (2019). “Mast cells, stress, fear, and autism spectrum disorder.” IJMS, 20(15), 3611.
Research Finding 3 — MCAS, ADHD, and Neuroinflammation
Research published in Experimental and Therapeutic Medicine found that mast cell-mediated neuroinflammation may disrupt the prefrontal dopamine and noradrenaline systems — the exact same systems that govern attention and executive function, and that are targeted by ADHD medication. Histamine, released by activated mast cells, directly affects brain function in ways that mirror and potentially worsen ADHD symptoms.
Source: Song, Y., et al. (2020). “Mast cell mediated neuroinflammation may have a role in ADHD.” Experimental and Therapeutic Medicine, 20(2), 714–726.
Research Finding 4 — The EDS/POTS/MCAS/ND Cluster
A large Swedish population study found that people with Ehlers-Danlos Syndrome — which frequently co-occurs with MCAS — were 7.4 times more likely to be autistic and 5.6 times more likely to have ADHD compared to matched controls. Elevated rates were also found in unaffected siblings, suggesting the clustering has a genetic basis rather than simply being a response to living with chronic illness.
Source: Hope Affirm Thrive clinical review (March 2026), citing Swedish population cohort study on EDS and neurodivergence.
Research Finding 5 — MCAS and Neuropsychiatric Symptoms
A 2023 case series published in the Journal of Personalized Medicine documented eight patients with significant neuropsychiatric disorders including ADHD, OCD, anxiety, depression, and panic disorder — all of whom had unrecognized MCAS. When mast-cell-directed treatment was initiated, neuropsychiatric symptoms improved. The authors noted MCAS is estimated to affect up to 17% of the population and patients can suffer for decades without recognition.
Source: Weinstock, L.B., Nelson, R.M., & Blitshteyn, S. (2023). Journal of Personalized Medicine, 13(11), 1562.
Research Finding 6 — Histamine, Allergies, and Neurodivergence
A large study published in Scientific Reports in 2021 found that children with ADHD or autism were significantly more likely to have allergic conditions including eczema, food allergies, and hay fever — conditions driven by the same histamine and mast cell activity implicated in MCAS. This suggests a shared immune dysregulation pathway across neurodivergent conditions.
Source: Scientific Reports (2021) population study on allergic conditions and neurodevelopmental diagnoses.
Why This Goes Unrecognized for So Long
If the connection between MCAS and neurodivergence is real and backed by research, why don't more people know about it? The answer is familiar to anyone who has spent time navigating the medical system as a neurodivergent person: the symptoms are diffuse, they fluctuate, they overlap with mental health diagnoses, and the patients reporting them are frequently dismissed.
MCAS patients can suffer for decades without recognition, in part because their symptoms touch so many body systems that no single specialist sees the full picture. Add to that the reality that autistic and ADHD adults are already frequently told their physical symptoms are "anxiety," "stress," or "just how they are" — and you have a perfect storm of missed diagnoses.
“Autistic and ADHD adults are already frequently told their physical symptoms are anxiety, stress, or just how they are. MCAS adds another invisible layer to an already invisible experience.”
The sensory hypersensitivity that is a hallmark of autism may in some individuals be compounded by — or partially explained by — mast cell activation in the nervous system. The brain fog, fatigue, and emotional dysregulation that autistic and ADHD adults experience may have both neurological AND immunological roots. These are not competing explanations. They may be deeply interconnected ones.
Symptoms That May Overlap — What to Pay Attention To
The following is not a diagnostic checklist — please do not use it as one. It is offered as a framework for noticing patterns worth discussing with a knowledgeable physician. Many of these symptoms are common in autistic and ADHD adults independently; what raises the possibility of MCAS is when they cluster together, fluctuate, and seem to respond to environmental or dietary triggers.
Symptom Overlap — Gastrointestinal
Chronic nausea, IBS-like symptoms, food sensitivities, bloating, abdominal pain — particularly if symptoms fluctuate and don’t respond consistently to dietary changes.
Symptom Overlap — Neurological and Cognitive
Brain fog, cognitive dysfunction, difficulty with word retrieval, memory issues — beyond what executive function challenges alone would explain.
Symptom Overlap — Sensory and Skin
Heightened sensory sensitivity, skin reactions including flushing, hives or itching without clear cause, reactions to heat, cold, or physical pressure.
Symptom Overlap — Cardiovascular and Autonomic
Heart palpitations, dizziness upon standing, POTS-like symptoms — particularly if co-occurring with hypermobility or EDS features.
Symptom Overlap — Mood and Psychiatric
Anxiety, depression, panic, mood instability — particularly when symptoms fluctuate in ways that don’t respond fully to standard psychiatric treatment and seem connected to physical triggers.
What This Means for Neurodivergent Adults
The research on MCAS and neurodivergence is still developing. We do not yet have definitive answers about causation, prevalence, or treatment pathways specifically tailored to autistic and ADHD individuals. What we do have is enough evidence to say: if you are neurodivergent and you have been living with unexplained physical symptoms, this is worth exploring with an informed physician — ideally one who understands both immunology and neurodivergence.
As a mental health clinician I sit at a particular intersection with this research. I see the downstream psychological effects of years of unrecognized physical illness — the self-doubt, the internalized shame of being told your symptoms are psychosomatic, the exhaustion of having to advocate for yourself in every medical setting. I also see what happens when people finally get answers. The relief of having language for your experience is profound. The ability to say "there is a biological mechanism here" can be the beginning of a fundamentally different relationship with your own body.
You were not making it up. You were not catastrophizing. Your body has been trying to tell you something. The research is finally beginning to catch up.
“You were not making it up. You were not catastrophizing. Your body has been trying to tell you something. The research is finally beginning to catch up.”
If you are a neurodivergent adult in California navigating questions about your mental and physical health from a whole-body perspective, Brightmane Therapeutic Center offers neurodivergent-affirming therapy in person in Willow Glen, San Jose and virtually throughout California. While we do not diagnose or treat MCAS, we specialize in supporting autistic and AuDHD adults in understanding their nervous systems, building self-advocacy skills, and healing from years of being unseen.
References
1. ScienceDirect. (June 2025). “The role of mast cells in Autism Spectrum Disorder.” Neuroscience & Biobehavioral Reviews.
2. Theoharides, T.C., et al. (2019). “Mast cells, stress, fear, and autism spectrum disorder.” IJMS, 20(15), 3611.
3. Song, Y., et al. (2020). “Mast cell mediated neuroinflammation may have a role in ADHD.” Experimental and Therapeutic Medicine, 20(2), 714–726.
4. Weinstock, L.B., Nelson, R.M., & Blitshteyn, S. (2023). “Neuropsychiatric Manifestations of MCAS.” Journal of Personalized Medicine, 13(11), 1562.
5. Scientific Reports. (2021). Population study on allergic conditions and neurodevelopmental diagnoses.
6. Kustow, J. (February 2025). “The Surprising Association Between ADHD & Inflammation.” ADDitude Magazine Webinar #545.
7. Hope Affirm Thrive Clinical Review. (March 2026). Citing Swedish population cohort study on EDS, autism, and ADHD co-occurrence.
Where Every Mind Belongs™
— Brightmane Therapeutic Center
Alisha Allen, LCSW · Brightmane Therapeutic Center · San Jose, CA
