Neurotransmitter-based diagnosis and treatment: A hypothesis (Part 3)

Optimal diagnosis and treatment of psychiatric illness requires clinicians to be able to connect mental and physical symptoms. Direct brain neurotransmitter testing is presently in its infancy and the science of defining the underlying mechanisms of psychiatric disorders lags behind the obvious clinical needs. We are not yet equipped to clearly recognize which neurotransmitters cause which symptoms. In this article series, we suggest an indirect way of judging neurotransmitter activity by recognizing specific mental and physical symptoms connected by common biology. Here we present hypothetical clinical cases to emphasize a possible way of analyzing symptoms in order to identify underlying pathology and guide more effective treatment. The descriptions we present in this series do not reflect the entire set of symptoms caused by the neurotransmitters we discuss; we created them based on what is presently known (or suspected). Additional research is needed to confirm or disprove the hypothesis we present. We argue that in cases of multiple psychiatric disorders and chronic pain, the development and approval of medications currently is based on an umbrella descriptive diagnoses, and disregards the various underlying causes of such conditions. Similar to how the many types of pneumonias are treated differently depending on the infective agent, we suggested the same possible causative approach to various types of depression and pain.

Part 1 of this series (Current Psychiatry, May 2022) looked into serotonin- and dopamine-associated symptoms. In Part 2 (Current Psychiatry, June 2022), we presented cases related to endorphin and norepinephrine dysfunction. We conclude the series by exploring gamma aminobutyric acid (GABA)- and glutamate-based clinical symptoms. Table 1 outlines medical and psychiatric symptoms that likely reflect GABA excess^1-9 and deficiency,^1-4,6,9-17 and Table 2 lists symptoms that likely reflect glutamate excess^9,18-31 and deficiency.^9,32-38 It is essential to note that both the quantity of neurotransmitters as well as the quality of the transmission (as in receptors, cellular pumps, and distribution mechanisms) are important.

GABA excess (Table 1^1-9)

Ms. V is brought to your office by a friend. She complains of pain all over her body, itchiness, inability to focus, and dizziness.^1,5,6,9 She is puzzled by how little pain she feels when she cuts her finger but by how much pain she is in every day, though her clinicians have not discovered a reason for her pain.^1,6,9 She states that her fatigue is so severe that she can sleep 15 hours a day.^1-6,9 Her obstructive and central sleep apnea have been treated, but this did not improve her fatigue.^3,5,9 She is forgetful and has been diagnosed with depression, though she says she does not feel depressed.^1,5,6 Nothing is pleasant to her, but she is prone to abnormal excitement and unpredictable behavior.^1,4,6,7

A physical exam shows slow breathing, bradycardia, decreased deep tendon reflexes, and decreased muscle tone.^1,5,6,9 Ms. V complains of double vision^1,5,6,9 and problems with gait and balance,^5,6,9 as well as tremors.^1,4-7 She experienced enuresis well into adulthood^1,5,6,9 and is prone to weight gain, dyspepsia, and constipation.^8,9 She cannot understand people who have anxiety, and is prone to melancholy.^4-6,9 Ms. V had been treated with electroconvulsive therapy in the past but states that she “had to have so much electricity, they gave up on me.”

Impression. Ms. V exhibits multiple symptoms associated with GABA excess. Dopaminergic medications such as methylphenidate or amphetamines may be helpful, as they suppress GABA. GABAergic medications and supplements should be avoided in such a patient. Noradrenergic medications including antidepressants with corresponding activity or vasopressors may be beneficial. Suppression of glutamate increases GABA, which is why ketamine in any formulation should be avoided in a patient such as Ms. V.

GABA deficiency (Table 1^1-4,6,9-17)

Mr. N complains of depression,^{1,3,4,6,12,16} pain all over his body, tingling in his hands and feet,^1,6,9 a constant dull headache,² and severe insomnia.^2,3,9,10 He cannot control his anxiety and, in general, has problems relaxing. In the office, he is jumpy, tremulous, and fidgety during the interview and examination.^1,3,4,6,9,12 His muscle tone is high^1,9,11 and he feels stiff.^6,9 Mr. N’s pupils are narrow^1,9; he is hyper-reflexive^1,9,11 and reports “Klonopin withdrawal seizures.”^1,6,9 He loves alcohol because “it makes me feel good” and helps with his mind, which otherwise “never stops.”^1,6,13 Mr. N is frequently anxious and very sensitive to pain, especially when he is upset. He was diagnosed with fibromyalgia by his primary care doctor, who says that irritable bowel is common in patients like him.^1,6 His anxiety disables him.^1-4,6,9-12 His sister reports that in addition to having difficulty relaxing, Mr. N is easily frustrated and sleeps poorly because he says he has racing thoughts.¹⁰ She mentions that her brother’s gambling addiction endangered his finances on several occasions^4,12,15 and he was suspected of having autism spectrum disorder.^4,12 Mr. N is frequently overwhelmed, including during your interview.^1,3,4,6 He is sensitive to light and noise^1,9 and complains of palpitations^1,3,4,6,9 and frequent shortness of breath.^1,3,4,9 He mentions his hands and feet often are cold, especially when he is anxious.^1,3,4,6,9 Not eating at regular times makes his symptoms even worse. Mr. N commonly feels depressed, but his anxiety is more bothersome.^{1,3,4,6,12,16} His ongoing complaints include difficulty concentrating and memory problems,^3,4,12,13 as well as a constant feeling of being overwhelmed.^1,3,4,6 His restless leg syndrome requires ongoing treatment.^1,9,14 Though uncommon, Mr. N has episodes of slowing and weakness, which are associated with growth hormone problems.¹⁶ In the past, he experienced gut motility dysregulation^9,10 and prolonged bleeding that worried his doctors.¹⁷

Impression. Mr. N shows multiple symptoms associated with GABA deficiency. The deficiency of GABA activity ultimately causes an increase in norepinephrine and dopamine firing; therefore, symptoms of GABA deficiency are partially aligned with symptoms of dopamine and norepinephrine excess. GABAergic medications would be most beneficial for such patients. Anticonvulsants (eg, gabapentin and pregabalin) are preferable. Acamprostate may be considered. For long-term use, benzodiapines are as problematic as opioids and should be avoided, if possible. The use of opioids in such patients is especially counter­productive. Some supplements and vitamins may enhance GABA activity. Avoiding bupropion and stimulants would be wise. Ketamine in any formulation would be a good choice in this scenario. Sedating antipsychotic medications have a promise for patients such as Mr. N. The muscle relaxant baclofen frequently helps with these patients’ pain, anxiety, and sleep.

Continue to: Glutamate excess