Drowsiness causes an estimated 100, 000 car crashes in the U.S. each year, according to the National Highway Traffic Safety Administration, and kills 1, 500.

FORBES: Who's making big bucks off your insomnia?

Avoid taking valerian at the same time as medication that can cause drowsiness, as the effects could be additive, adds Massachusetts General's Dr. Ulbricht.

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It's even possible that, like Claritin, it wouldn't cause drowsiness--although extensive study would be necessary to find that out.

FORBES: Pharmaceuticals

Next in Terlings Park's pipeline is an antianxiety drug that may have the benefits of Valium without the accompanying drowsiness, temporary memory loss and habit-forming effects.

FORBES: Betting on the brain