We outline connections between the gut microbiome, autoimmune conditions, neuropathic pain, eye pain, chemical intolerance, and a specific set of “overactive” mental illnesses. All seem to be connected to a sensory processing disorder. This is joint work with Luca Estinto.

Sensory processing disorders and connectivity

People who react strongly to perfumes and strong smells (chemical intolerance) are such that they perceive a smell at a constant level of intensity, the signal is processed at the same intensity over time. Normal people perceive the signal intensity to decrease over time, they “get used to it”. Signal intensity is monitored via brain blood flow (measured using EEG and fMRI). The same blood flow pattern as those with chemical intolerance is found in those with chronic pain. [(2012)Summary of Linuss Andersson (Sick of Smells: Empirical Findings and a Theoretical Framework for Chemical Intolerance)] [(2018) Multiple Chemical Sensitivity Review of the State of the Art in Epidemiology, Diagnosis, and Future Perspectives].

Sensory processing disorders and glutamate

If you want to imagine what life is like as a highly sensitive person recall what it is like to have a hangover — when you have a hangover you have an excess of free glutamate which causes overexcitability of sensory processing.

Children with sensory processing disorders have disconnected white matter (measured using DTI) [(2016)Brain’s Wiring Connected to Sensory Processing Disorder].

Excitable Mental Illness and the role of Glutamate

A sensory processing disorder makes excitable mental illnesses more likely. Mental illness wise, adhd, aspergers, bipolar, anxiety and autism have “ring of fire” blood flow patterns in the brain. Too much glutamate causes overexcitability of the brain (measured using SPECT). [Amen Clinics Articles] Their clinic uses SPECT imaging as a diagnostic tool for psychiatric treatment [Amen Clinics: Multi-site six month outcome study of complex psychiatric patients evaluated with addition of brain SPECT imaging]. Some examples (all photos are from the Amen Clinic):

Sensory processing disorders and Autoimmune Disease

People who are highly sensitive (a genetic trait) are more likely to have autoimmune diseases such as diabetes, and I would postulate, celiac. [(2018)Sensory Processing Sensitivity and Type 1 Diabetes] [Celiac and Diabetes are often comorbid]

SPD causing Visual Tunneling and Autoimmune conditions affecting Eyesight

Further, nutrient deficiences such as low vitamin D as well as being sensorily overwhelmed cause eyesight issues (autoimmune diseases of the eye and visual tunneling respectively) [source?]. Visual tunneling is a particularly pervasive issue that affects all senses. [(2014)Visual Tunneling: A Pervasive Vision disorder]

Enteric Nervous System and Mental Illness

Our guts produce 90% of serotonin, if you are low on folic acid or any other basic vitamins/nutrients you literally cannot create serotonin, dopamine, and other neurotransmitters. [add] Would a severe serotonin deficiency show up in a SPECT scan?

There is ongoing work to directly detect and monitor this for diagnostic and treatment purposes. [UMD: building an ingestible capsule that can monitor and model gut microbiome serotonin activity]

Enteric Nervous system/SPD causing Lowered Immune System causing Autoimmune Disease

If you have a lower immune system (low igA or igG or igM) you are more likely to have an autoimmune disease.

Remark: As a note, you are also more likely than average to have an autoimmune disease with an abnormally strong immune system. This is not the case we are discussing here.

The enteric nervous system generates igA and igG in our body [add]. This is why heightened igA and igG are a ridiculous diagnostic criterion for celiac disease [(2017)Lack of Utility of Anti-tTG IgG to Diagnose Celiac Disease When Anti-tTG IgA Is Negative].

People with IgA deficiency should be tested for celiac disease because they are 10 to 20 times likely to develop an autoimmune response to gluten than the general population. [6]

Immunosenescence or the ageing of the immune system is linked to the increase of autoantibody frequency while the antibodies decline [(2004) The Neuroendocrine Immune Network in Ageing ].  One way to frame the connection between SPD and being immunocompromised is that higher sensitivity leads to greater stress / perceived stress, which leads to a decrease in immunity which then naturally causes an increase in autoantibodies that would otherwise have occured during someones natural immunosenescence. [(2004) Inflamm-aging: autoimmunity, and the immune-risk phenotype ]

Mechanisms of Functional Dyspepsia and Treatment with Tricyclic Antidepressent

A proposed mechanism is that there is original inflammation, and then continued faulty pain signaling when input is gone. That is, a central sensitization model. [(2002) Functional dyspepsia–a psychosomatic disease ][Functional Dyspepsia: A Review of the Symptoms, Evaluation, and Treatment Options ] [(2005-2015) Antidepressent Therapy for Function Dyspepsia ] [(2018) Antidepressants improve functional dyspepsia symptoms, but how remains unclear ]

[add] IBS treatment with known placebo trial

Enteric Nervous System and Excitable Mental Illness

There has been some recent research on fecal transplants curing some forms of mental illness. The inverse is also true “with the transmission of depressive and anxiety-like symptoms and behaviours resulting from the transplantation of microbiota from psychiatrically ill donors to healthy recipients”.
[(2020) Effect of fecal microbiota transplant on symptoms of psychiatric disorders: a systematic review ] [(2020) 7: Fecal Microbiota Transplantation in Depression] [(2019) Posttraumatic stress disorder is associated with altered gut microbiota that modulates cognitive performance in veterans with cirrhosis ] [(2019-2021) Examining Changes in Microbiota Over the Course of PTSD Treatment].

Keyword summary:

• visual tunneling
• chemical intolerance
• chronic pain
• excess free glutamate
• high sensitivity
• autism/ocd/add/ptsd/bipolar
• functional dyspepsia
• sensory processing disorder.
• low autoimmune system
• likelihood to have autoimmune disease
• enteric nervous system
• lowered ability to create serotonin
• joint hyperflexibility