Lemon Balm

• GABA system modulation. Lemon balm extracts (especially rosmarinic acid and triterpenes such as ursolic and oleanolic acid) inhibit GABA-transaminase (GABA-T) in vitro, which can increase GABA levels in the brain — a plausible anxiolytic mechanism (GABA is the major inhibitory neurotransmitter). Europe PMC
• Cholinergic and receptor effects. Some preparations show binding/activity at cholinergic and GABA_A receptor systems and affect nicotinic/muscarinic receptors; essential oil components (citral, citronellal, geraniol, etc.) may also contribute to calming effects. Northumbria University Research Portal
• Anti-inflammatory / antioxidant compounds. Rosmarinic acid and flavonoids have neuroprotective/anti-inflammatory properties that could indirectly support mood regulation. ScienceDirect

Summary: biochemical data + animal/in vitro work identify plausible mechanisms (GABA-T inhibition, receptor modulation) which support the clinical signals seen in human trials, but those clinical trials are relatively small and heterogeneous. Europe PMC

Forms used in trials:

• Standardised extracts / capsules / tablets — most clinical trials use standardised extracts (mg doses quoted below). MDPI
• Drinks / foods (beverage, yoghurt) — some studies used an extract mixed into a beverage or yoghurt to test acute mood effects. MDPI
• Tea (dried leaves) — common traditional use; clinical dosages more often reported for extracts than tea.

Common clinical doses (examples from trials and reviews):

• Acute single doses: 300–900 mg extract (single dose) used in crossover studies that measured short-term mood/cognition effects (e.g., Kennedy et al.). Effects on stress/anxiety were reported within 1–3 hours. Northumbria University Research Portal
• Daily extract doses (short-term courses): studies have used 600–1,600 mg/day (various extracts) and reported benefits in mood/anxiety measures. Drugs.com
• Higher/longer dosing in some trials: one RCT in patients with chronic stable angina used 3 g/day of M. officinalis (crude supplement) for 8 weeks and measured anxiety/stress outcomes. Clinical Nutrition ESPEN

Practical, evidence-based usage recommendations (based on how it was studied):

• For acute situational anxiety / lab-induced stress: a single 300–600 mg standardised extract has been used and shown short-term calming effects in young healthy adults. Consider one dose taken 30–90 minutes before the stressful event (as per acute studies). Northumbria University Research Portal
• For ongoing mild anxiety or mixed anxiety/depressive symptoms: trials and meta-analyses commonly used daily extract doses in the 600–1,600 mg/day range divided across the day; some studies used up to 3 g/day of crude preparations. Typical course lengths in RCTs: 2–8 weeks. Drugs.com
• Tea (traditional use): steep 1–2 g dried leaves (≈1 tsp) in hot water for 5–10 minutes, 1–3 cups daily — used traditionally, but note that standardisation and rosmarinic acid content vary widely (so effects seen in trials of standardised extracts may not exactly match tea). MDPI

If you try lemon balm clinically:

• Prefer standardised extracts (products that state rosmarinic acid content) for reproducibility. MDPI
• Start with a low dose (for example 300 mg extract once daily) to assess tolerance, then increase if needed toward the ranges above and under medical supervision. (This is a practical, conservative recommendation consistent with how trials titrated effects.) 

Systematic review & meta-analysis

• Ghazizadeh J. et al. — “The effects of lemon balm (Melissa officinalis L.) on depression and anxiety in clinical trials: A systematic review and meta-analysis” (Phytotherapy Research, 2021) — pooled RCTs and reported that lemon balm preparations show promise for improving acute anxiety/depressive symptoms but noted heterogeneity and small trials; useful summary of human evidence. Deakin Research Online

Notable randomized human trials

• Kennedy et al., Neuropsychopharmacology / Psychosomatic Medicine (early 2000s). Randomised, placebo-controlled, crossover studies of single doses (300–900 mg) of standardized Melissa extract in healthy adults reported improvements in mood and attenuation of lab-induced stress. These are widely cited as early evidence of acute anxiolytic/mood effects. Northumbria University Research Portal
• Clinical Nutrition / other RCTs — e.g., a double-blind RCT used 3 g/day MO for 8 weeks in patients with chronic stable angina and measured depression/anxiety/sleep outcomes (showed improvements in some measures). Clinical Nutrition ESPEN
• Multiple smaller RCTs (various extracts, doses, durations) exist — several compared lemon balm vs placebo or vs comparators (including combined formulas such as lemon balm + valerian for sleep). The systematic review above pooled many of these. Bond University Research Portal