5-HTP is the intermediate metabolite of the essential amino acid L-tryptophan and the immediate final precursor in the biosynthesis of 5-hydroxytryptamine, which, along with dopamine and norepinephrine, are the three major monoaminergic neurotransmitters. Serotonin production is linked to insomnia (sleep disturbances), anxiety, nervousness, sugar cravings, appetite suppression, chronic and tension headaches, depression, low mood, fibromyalgia, obesity, and aggression.