As a sedative, valerian works safely and gently to help calm nerves and promote physical relaxation without the presence of an altered state like you would expect from a prescription sedative.

Helpful for reliving nervousness and restlessness, stress, anxiety, nervous exhaustion, bronchial spasms, stomach crapms, colic, flatulence, constipation.

In the digestive tract Valerian is helpful as a antispasmodic for situations where nervousness is compounded by a spastic colon or an upset stomach.  Can also help lower blood pressure.
NB: Valerian is a banned substance under most equestrian associations.