Neurotransmitter-based diagnosis and treatment: A hypothesis (Part 1)

It is unfortunate that, in some clinical areas, medical conditions are still treated by name and not based on the underlying pathological process. It would be odd in 2022 to treat “dropsy” instead of heart or kidney disease (2 very different causes of edema). Similarly, if the FDA had been approving drugs 150 years ago, we would have medications on label for “dementia praecox,” not schizophrenia or Alzheimer disease. With the help of DSM-5, psychiatry still resides in the descriptive symptomatic world of disorders.

In the United States, thanks to Freud, psychiatric symptoms became separated from medical symptoms, which made it more difficult to associate psychiatric manifestations with the underlying pathophysiology. Though the physical manifestations that parallel emotional symptoms—such as the dry mouth of anxiety, the tremor and leg weakness of fear, the constipation and blurry vision of depression, the breathing difficulty of anger, the abdominal pain of stress, the blushing of shyness, the palpitations of flashbacks, and endless others—are well known, the present classification of psychiatric disorders is blind to it. Neurochemical causes of gastrointestinal spasm or muscle tension are better researched than underlying central neurochemistry, though the same neurotransmitters drive them.

Can the biochemistry of psychiatric symptoms be judged on the basis of peripheral symptoms? Can the mental manifestations be connected to biological causation, and vice versa? Would psychiatrists be better off selecting treatments by recognizing involved neurotransmitters instead of addressing descriptive “depression, anxiety, and psychosis”? Each of these clinical syndromes may be caused by entirely different underlying neuronal mechanisms. Such mechanisms could be suggested if medical symptoms (which are measurable and objective) would become part of the psychiatric diagnosis. Is treating the “cough” sufficient, or would recognition that tuberculosis caused the cough guide better treatment? Is it time to abandon descriptive conditions and replace them with a specific “mechanism-based” viewpoint?

Ample research has shown that serotonin, dopamine, norepinephrine, endorphins, glutamate, and gamma aminobutyric acid (GABA) are the neurotransmitters most responsible in the process of both psychiatric disorders and chronic pain. These neuro­transmitters are involved in much more than emotions (including the feeling of pain). An abundance of medical symptom clusters point toward which neurotransmitter dysfunction may be leading in specific cases of distinct types of depression, psychosis, anxiety, or “chronic pain.” Even presently, there are medications available (both for FDA-approved indications and off-label) that can be used to regulate these neurotransmitters, allowing practitioners to target the possible biological underlining of psychiatric or pain pathology. Hopefully, in the not-so-distant future, there will be specific medications for serotonin, dopamine, and noradrenergic depression as well as for GABAergic anxiety, endorphin psychosis, noradrenergic insomnia, and similar conditions.

Numerous neurotransmitters may be connected to both depression and pain in all their forms. These include (but are not limited to) prostaglandins, bradykinins, substance P, potassium, magnesium, calcium, histamine, adenosine triphosphate, calcitonin gene-related peptide (CGRP), nitric oxide (NO), cholecystokinin 7 (CCK7), neurotrophic growth factor (NGF), neurotensin, acetylcholine (Ach), oxytocin, cannabinoids, and others. These have not been researched sufficiently to identify their clinical presentation of excessive or insufficient availability at the sites of neurotransmission. It is difficult to draw conclusions about what kind of clinical symptoms they may cause (outside of pain), and therefore, they are not addressed in this article.

Both high and low levels of certain neuro­transmitters may be associated with psychiatric conditions and chronic pain. Too much is as bad as too little.¹ This applies to both quantity of neurotransmitters as well as quality of the corresponding receptor activity. An astute clinician may judge which neurotransmitter is dysfunctional based on the patient’s presentation. Reading indirect signs of bodily functions is a basic clinical skill that should not be forgotten, even in the time of advanced technology.

A different way of viewing psychiatric disorders

In this article, we present 4 hypothetical clinical cases to emphasize a possible way of analyzing symptoms to identify underlying pathology and guide more effective treatment. In no way do these descriptions reflect the entire set of symptoms caused by neurotransmitters; we created them based on what is presently known or suspected, and extensive research is required to confirm or disprove what we describe here.

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