GAD (glutamic acid decarboxylase) antibodies are expressed in type 1 (autoimmune) diabetes, adrenal failure (Addison disease), autoimmune thyroid diseases, premature ovarian failure, myasthenia gravis, pernicious anemia, Stiff-man syndrome and a number of other disorders. An informative study recently published in Acta Neurologica Scandinavica documents the link between these conditions and gluten sensitivity. The authors state:

“The high prevalence of gluten sensitivity in patients with stiff-person syndrome (SPS) lead us to investigate the relationship between gluten sensitivity and GAD-antibody-associated diseases.”

They used ELISA assays for GAD antibodies and serological markers of gluten sensitivity that generated compelling data:

“”Six of seven (86%) patients with SPS were positive for anti-GAD…This compared with 9/90 (11%) patients with idiopathic sporadic ataxia…16/40 (40%) patients with gluten ataxia…and 6/10 patients with type 1 diabetes only…”

Note that the serological tests for gluten sensitivity are a blunt instrument—only 40% of confirmed cases of gluten ataxia were recognized. The abundance of false negatives is why the gluten gene sensitivity test is so valuable.

Additionally, the authors found that…

“The titre of anti-GAD reduced following the introduction of a gluten-free diet in patients with SPS who had serological evidence of gluten sensitivity.”

Their conclusion is simply stated:

“These findings suggest a link between gluten sensitivity and GAD antibody-associated diseases.“

This study is especially interesting in connection with earlier research published in the journal Psychiatry. The authors set out to investigate the role of GAD antibodies in schizophrenia and related disorders:

“We hypothesized that GAD antibodies are increased in patients with chronic psychotic disorders. The aim of this pilot study was to compare the level of GAD antibodies in patients with chronic psychotic disorders with normal controls.”

By way of background they note that:

“The role of GABAergic neurotransmission in epilepsy, anxiety disorders, schizophrenia, and premenstrual dysphoric disorder has been a subject of some recent investigations. Absence of structural abnormalities in the brains of most patients with chronic psychotic disorders has always raised suspicion for an alternative pathogenesis and a possible functional disturbance at the neuronal/cellular level. Glutamic acid decarboxylase (GAD)…is involved in the formation of gamma aminobutyric acid (GABA) a central inhibitory neurotransmitter of the nervous system. Antibodies to GAD may impair GABA formation or inhibitory function.“

What did the data show?

“Serum levels of GAD antibodies in 12 patients with chronic psychotic disorders (schizophrenia and schizoaffective disorders) and 10 age-matched healthy control subjects were evaluated… Antibodies to GAD in patients with chronic psychotic disorders have a higher mean than nonpatient control individuals.”

The authors’ conclusion alerts the practitioner to be on the lookout:

“Antibodies to GAD65 are peripherally present in patients with chronic psychotic disorders (schizophrenia/schizoaffective disorders)... The presence of such antibodies also suggests a possible role for autoimmune mechanism in the pathogenesis of these disorders. In summary, from a practicing psychiatrist’s point of view, measurements of antibodies to GAD65 could potentially be used to screen for chronic psychotic disorders and for diabetes mellitus very early on in the disease process.”

GAD (glutamic acid decarboxylase) produces GABA, the most abundant inhibitory (calming) neurotransmitter in the body. Suboptimal levels can manifest as anxiety, insomnia, hyperarousal, panic, feeling overwhelmed, disorganized attention, restlessness, worry, tension, inner excitability, inability to relax, etc.