Passionflower is considered a systemic anti-anxiety herb, meaning regular use over a period of time helps the nervous system calm down. Quicker and stronger natural remedies would be kava
and holy basil -- the first works on GABA, probably, and the second works on cortisol production, which creates the physiological symptoms of anxiety. Herbs that balance the adrenals, such as ashwagandha, might help as well. Valerian also helps some people.