Derived from the root of the plant V. officinalis, valerian is sold as a dietary supplement for calmness, sedation, and to improve sleep quality. Other species including V. jatamansi, V. fauriei, and V. wallichii are also used in traditional medicine to treat insomnia and anxiety. Valerian products are usually available in extracts or teas that have a distinct odor.

In vitro, valerian exhibits antioxidant ⁽¹⁾, cytoprotective ⁽²⁾, and neuroprotective ⁽³⁾ effects. In animal models, valerian has demonstrated antihypertensive, antispasmotic ^(4) (5), anxiolytic ⁽⁶⁾, and antidepressant ⁽⁷⁾, but not sedative ⁽⁸⁾ effects.

Human studies show that valerian has modest effects on improving sleep quality ^{(9) (10) (11)}, but its sleep-inducing properties are not superior to placebo ^{(12) (13) (14) (15)}. Valerian also failed to improve sleep in a study of cancer patients ⁽¹⁶⁾. Other studies suggest that valerian may improve sleep and anxiety in HIV patients on antiretroviral therapy ⁽⁵³⁾, reduce hot flashes ^(17) (54) and dysmenorrhea ⁽¹⁸⁾, facilitate supervised benzodiazepine withdrawal ⁽¹⁹⁾, and relieve symptoms of obsessive-compulsive disorder ⁽²⁰⁾. However, sample sizes in these studies are too small to draw firm conclusions. Reviews of the clinical literature have also concluded the evidence for valerian as an anxiolytic in humans is insufficient ^(21) (22).

The valerian derivative isovaleroxy-hydroxy dihydrovaltrate showed anticancer effects against human ovarian cancer cells in vitro and in vivo ⁽²³⁾. Chlorovaltrates in valerian have shown moderate cytotoxicity against lung, prostate, colon and liver cancer cell lines ⁽²⁴⁾. However, no clinical trials on these effects have been conducted.

Although valerian products are generally safe, cases of liver and pancreatic toxicity have been reported ^{(25) (26) (27)}. Valerian is also thought to have estrogenic activities ^(17) (28), but this was not observed in vitro ⁽²⁹⁾.