GABA and sleep latency: grade C

A 2020 systematic review of 14 placebo-controlled trials found very limited evidence for sleep benefits. Two single-blind crossover studies in 10 and 16 poor sleepers, run by researchers employed by the supplier Pharma Foods International, reported shorter sleep latency with 100 mg; the second abstract gives no comparison with placebo. In a double-blind trial of 40 adults with insomnia symptoms funded by the supplier Natural Way, 300 mg for 4 weeks shortened sleep latency on polysomnography with a significant group-by-time interaction, but the placebo group had only 10 people and baseline sleep differed between groups. A second trial from the same group (54 adults, 75 mg) found the change was not significant relative to placebo. All four trials were industry-run or industry-funded, and those with a stated length lasted 1 to 4 weeks. Only one small single-blind crossover and one imbalanced double-blind trial were positive against placebo, so the proposal is C with direction none (limited, mixed).

How we grade evidence