For many individuals, valerian, passionflower, and chamomile are viewed as the most effective calming herbs based on subjective ratings; however, the evidence varies greatly on their effectiveness and most users will find that they provide mild to moderate effects. These herbs may interact with other medications (sedatives), alcohol and may not be safe for pregnant women. It is recommended to use low dosages of these herbs (if at all) and to verify the safety of any of them before using them if you are unsure.