L-Tryptophan has been used in the treatment of insomnia, anxiety and depression as well as for appetite supression and  other problems.

Dosage:The dosage range for for L-Tryptophan is 500-2000mg per day and should be taken between meals.
Precautions : Do not use in combination with 5-HTP or  Selective Serotonin Reuptake Inhibitors (SSRIs) such as Prozac, Paxil, Zoloft, etc.