The September issue of Consumer Reports will rank supplements and herbs, I'm looking forward to what they have to say on the subject.
Stress and anxiety produce a ton of inflammatory hormones. Inflammation and anxiety kinda feed off each other and can make anxiety worse, not to mention what chronic low grade inflammation can do to your health. Your doc can test your inflammation levels with a common screening test called "high-sensitivity C-reactive protein" or HS-CRP. Foods high in omega-3 fatty acids can help lower inflammation, as do ginger, turmeric and extra virgin olive oil.
(CR will also list the 12 most dangerous: "aconite, bitter orange, chaparral, colloidal silver, coltsfoot, country mallow, germanium. greater celandine, kava, lobelia, and yohimbe")