Glycine

Inhibitory neurotransmitter action: Glycine is an inhibitory amino acid neurotransmitter in the spinal cord and brainstem (opens glycine-gated chloride channels). That inhibitory action can produce calming effects in neural circuits. ScienceDirect

NMDA co-agonist / modulatory site: Glycine is also an obligatory co-agonist at the NMDA glutamate receptor. Modulating the glycine site (either increasing glycine or blocking its reuptake) changes glutamatergic signalling and can affect mood, anxiety and cognition — this is why researchers study glycine and glycine-transporter inhibitors for psychiatric symptoms. Frontiers

Sleep-related effects that reduce anxiety: Multiple human studies show 3 g glycine before bedtime improves subjective sleep quality and next-day fatigue/“clear-headedness.” Better sleep frequently reduces anxiety symptoms (so some of glycine’s anxiolytic effects may be mediated indirectly through improved sleep). SpringerLink

• Typical clinical dosing (most human studies): 3 grams orally taken before bedtime is the common dose used in human sleep studies and many small clinical reports. Improvements in subjective sleep and daytime sleepiness were reported with 3 g. (If anxiety benefit derives from better sleep, this is the dose most evidence supports.) SpringerLink
• Duration in trials: Most human trials assessing sleep used single-night crossover designs or short courses (days to weeks). Some safety notes discuss up to 3 g/day for weeks; some sources report short trials using up to 6 g/day for 4 weeks without acute severe adverse events, but long-term safety data are limited. SpringerLink
• Form & timing: Oral glycine powder or capsules; taken shortly before sleep (studies usually gave it immediately before bedtime). For anxiety specifically, there’s no standardized regimen from large trials — the adjustment-disorder study used a proprietary microencapsulated glycine formulation (see studies below). Biotiki

Practical (evidence-based) suggestion used in studies (not medical advice): if a clinician agrees, many people trial 3 g orally at night (powder or capsule) for short-term use to assess effects on sleep and anxiety. Do not assume higher doses are safer or more effective — higher doses have less safety data. SpringerLink

Human sleep RCTs / crossover studies (3 g glycine before bedtime) — Inagawa et al. / related work — glycine ingestion improved subjective sleep quality and daytime function. These human volunteer studies are the best-replicated human data and support 3 g at bedtime. SpringerLink

Randomized, placebo-controlled study in adjustment disorder (mild anxiety presentation) — a randomized trial (microencapsulated glycine formulation) reported improvement in patients with adjustment disorder characterized by emotional disturbance. This is a relatively small / less widely circulated trial but directly assessed anxiety-type symptoms. (Paper originally reported from Russian group; see the randomized, placebo-controlled report). Biotiki

Preclinical & mechanistic reviews — Reviews on the glycine site of NMDA receptors and glycine transporter biology explain how glycine modulation can affect mood, cognition and anxiety-related circuits. These explain the mechanistic rationale for investigating glycine/glycine-transporter inhibitors in anxiety and mood disorders. ScienceDirect

Trials of glycine-transporter inhibitors (GlyT1 inhibitors) and related compounds — not plain glycine, but drugs that increase synaptic glycine (by blocking reuptake) have been trialed for panic disorder and other anxiety/psychiatric conditions; results are mixed and mainly experimental. These trials show the pathway is therapeutically interesting but not definitive. Psychiatrist.com

Recent papers on glycine’s role in mood disorders — newer basic research (e.g., work implicating glycine signalling and receptors in depression/anxiety physiology) has renewed interest in glycine-based approaches, but translational work is ongoing. Neuroscience News