A patient I'll call Rachel, a 24-year-old graduate student, described it perfectly: "My brain feels like it's revving even when nothing is happening." She wasn't in crisis. She was tired, wired, and unable to fully unwind, even in bed at midnight with the lights off. What Rachel was describing, in plain language, is a tilt in one of the most fundamental balances in the human brain: the ratio between glutamate and GABA.
The Brain's Balance Beam: Glutamate and GABA
Glutamate and GABA (gamma-aminobutyric acid) are the two most abundant neurotransmitters in the human brain, and they work in direct opposition to one another. Glutamate is the brain's primary excitatory signal. It speeds things up, sharpens alertness, and drives learning and memory. GABA is the brain's primary inhibitory signal. It slows things down, quiets neural firing, and produces the subjective sense of calm.
Neither system is "bad." A healthy brain needs both. The problem isn't glutamate itself, it's what happens when glutamate activity runs high relative to GABA for too long. Excess glutamate signaling is strongly associated with anxiety, irritability, racing thoughts, and difficulty falling or staying asleep. Too much GABA activity relative to glutamate, on the other hand, produces excessive drowsiness, sedation, and mental fog. Mood stability, in a very real neurochemical sense, is an equilibrium problem: keeping these two systems in proportion to one another rather than maximizing one over the other.
This is one of the reasons chronic stress is so corrosive to mental health. Sustained stress pushes the glutamate system into overdrive while GABA signaling struggles to keep pace, and the result is a nervous system stuck in a low-grade state of threat detection. Over time, that imbalance shows up as generalized anxiety, insomnia, and a shortened fuse for everyday frustrations.
Research Note
L-theanine, an amino acid concentrated in green tea, has been shown in human studies to reduce glutamate release at the synapse while supporting GABA-A receptor activity, producing what researchers describe as "relaxation without sedation." Randomized trials using 200 to 400 mg daily have documented measurable increases in calming alpha brain wave activity along with reductions in subjective stress and anxiety.
L-Theanine: Turning Down Glutamate
L-theanine works on both sides of the balance beam. It reduces the release of glutamate from presynaptic neurons, and some of that glutamate is then converted into GABA itself, nudging the whole system toward calm. Because it does this without directly sedating the brain, people who take it typically describe feeling settled and clear-headed rather than drowsy, which is why it's popular for daytime anxiety support as well as for winding down before bed.
In the clinical and research literature, the most consistently studied dose range for stress, anxiety, and sleep support is 100 to 400 mg per day, often taken as a single dose or split into two doses. Doses up to roughly 600 to 1,200 mg per day have been used safely in research settings, though most people find benefit well below that ceiling. As with any supplement, individual response varies, and higher doses should only be used under medical guidance, particularly for anyone on sedatives, blood pressure medication, or other psychiatric medications.
Apigenin: A Gentler Hand on the GABA-A Receptor
Apigenin is a plant flavonoid, most concentrated in chamomile, that takes a different route to the same destination. Rather than acting upstream on glutamate release, apigenin binds directly to the GABA-A receptor at a site closely related to the one benzodiazepine medications use. That binding enhances GABA's calming, inhibitory signal in the brain.
What makes apigenin clinically interesting is what it doesn't appear to do. Unlike benzodiazepines, it doesn't seem to produce significant sedation, muscle relaxation, or dependence at typical supplemental doses, which is part of why it's drawn attention as a gentler option for everyday anxiety and pre-sleep wind-down. Isolated apigenin supplements are typically dosed in the range of 25 to 50 mg, taken 30 to 60 minutes before the desired calming effect, with some products going up to 100 mg. Much of the strongest human evidence actually comes from chamomile extract studies rather than isolated apigenin, so it's worth treating the isolated-supplement dosing as reasonable but still an evolving area of research.
L-theanine and apigenin are also commonly paired together, since one dampens glutamate output while the other amplifies GABA's effect at the receptor, approaching the same balance point from two different directions.
Back to Rachel
For someone like Rachel, understanding this balance changes the conversation. Her racing thoughts at midnight weren't a personality flaw or a lack of willpower, they were a nervous system with glutamate activity outpacing GABA. Addressing that imbalance, alongside sleep hygiene, stress management, and when appropriate, other treatment, is often what finally lets the brain's built-in brake system do its job.
Struggling with anxiety, racing thoughts, or poor sleep?
Dr. Mark Agresti offers integrative psychiatric care combining conventional and nutritional approaches, in-person in Palm Beach and via telemedicine throughout Florida.
44 Cocoanut Row, Suite M202, Palm Beach, FL 33480 | (561) 760-4107 | DrMarkAgresti.com
This article is for educational purposes and does not constitute medical advice. Supplements can interact with medications and existing health conditions. Consult a psychiatrist or physician before starting any new supplement regimen.
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