Albizzia julibrissin by Ray Sahelian, M.D.

Albizzia julibrissin (Mimosa), traditionally known in China as the "herb of happiness," is one of the most valued Chinese botanicals for supporting a healthy mood during periods of occasional anxiety and stress. Albizzia flowers and bark have been used for centuries to elevate the mood, promote mental calmness, and support a peaceful night's sleep. See Chinese herbs for a list of herbs used in Chinese Medicine.
   There are several supplements used for mood enhancement or have an influence on happiness including SAM-e, 5-HTP, and St Johns Wort.

Planetary Herbals Albizzia Calm, 4 fl oz
Supports Mental Calmness
Herbal Supplement

I have not seen clinical trials with this herb as of 2011.