Evidence Level
Valerian is one of the most studied herbal sleep aids, though results are mixed due to heterogeneous study designs and preparations. Bent et al. (2006) conducted the most rigorous meta-analysis, analyzing 16 RCTs and concluding valerian improves subjective sleep quality without significant adverse effects. Leathwood & Chauffard (1985) demonstrated dose-dependent improvements in sleep latency and quality with aqueous extract. Fernández-San-Martín et al. (2010) performed a quantitative meta-analysis confirming a statistically significant improvement in sleep quality (OR 1.37). The mechanism is well-characterized: valerenic acid modulates GABA-A receptor beta-3 subunits (Benke et al., 2009), while other compounds inhibit GABA transaminase and GABA reuptake, collectively increasing GABAergic tone.