Valerian is a perennial plant native to Europe and Asia and now cultivated in North America. It has been used as a medicinal herb since ancient times, and has long been recognized as an aid to sleep. You can get it at health food stores, although like melatonin, it is not regulated and you never really know the strength in the bottles you get in the store. The valerian in dietary supplements comes from roots and stems. Sometimes people take the valerian as a tea-like beverage, and dried plant materials and extracts are put into capsules or incorporated into tablets. Some people advocate taking valerian with hops, the plant used to flavor beer, but there is no scientific evidence that this works.
Valerian appears to work for some people, althouth it is not a miracle compound for relief of insomnia. It has mild sedative and muscle-relaxant effects. Overall evidence that would recommend use is scant.
The results of some studies suggest that valerian may be useful for insomnia and other sleep disorders, results of other studies do not show any significant effect. The National Institutes of Health concluded that "the evidence from these trials for the sleep-promoting effects of valerian is inconclusive."
A recent test in rats found that valerian shortened the sleep latency period, but it apparently had no effect on REM/non-REM sleep splits and delta activity. The Japanese researchers concluded that valerian might help people get to sleep without altering the sleep cycle. A Spanish study in 2010 found insufficient evidence to recommend use of valerian or even of further study. A recent Norwegian study found the herb was safe with modest benefits - this study was notable mostly for its use of television and the internet.
In tests with Parkinson's disease patients, valerian use resulted in a mild decrease in sleep latency and an increase in total sleep time. A study on patients with arthritis-related sleep disturbances found valerian did not significantly help. A study on patients with restless leg syndrome found some positivie benefits of valerian.
Many chemical constituents of valerian have been identified, but scientist still don't know which compounds make people fall asleep. It is likely that there is no single active compound and that valerian's effects result from multiple constituents acting independently or together. Swiss scientists recently found brain elements that provide some clue to valerien's action. A specific binding site on Gaba(a) receptors with affinity for chemicals in valerian were identified.