Abstract
Sleep is an essential component of physical and emotional well-being, and lack, or disruption, of sleep due to insomnia is a highly prevalent problem. The interest in complementary and alternative medicines for treating or preventing insomnia has increased recently. Centuries-old herbal treatments, popular for their safety and effectiveness, include valerian, passionflower, lemon balm, lavender, and Californian poppy. These herbal medicines have been shown to reduce sleep latency and increase subjective and objective measures of sleep quality. Research into their molecular components revealed that their sedative and sleep-promoting properties rely on interactions with various neurotransmitter systems in the brain. Gamma-aminobutyric acid (GABA) is an inhibitory neurotransmitter that plays a major role in controlling different vigilance states. GABA receptors are the targets of many pharmacological treatments for insomnia, such as benzodiazepines. Here, we perform a systematic analysis of studies assessing the mechanisms of action of various herbal medicines on different subtypes of GABA receptors in the context of sleep control. Currently available evidence suggests that herbal extracts may exert some of their hypnotic and anxiolytic activity through interacting with GABA receptors and modulating GABAergic signaling in the brain, but their mechanism of action in the treatment of insomnia is not completely understood.