The extreme and often compulsive urges to pull that are associated with trichotillomania are often due to an underlying imbalance in brain chemicals called neurotransmitters. In regards to trichotillomania, the most important neurotransmitter imbalances seem to be between serotonin and the catecholamines (which include dopamine, norepinephrine and epinephrine). These neurotransmitters are made from amino acids.
Serotonin is synthesized in the brain from 5-hydroxytryptohan (or 5-HTP). Dopamine is made from L-tyrosine or L-dopa (L-3, 4-dihydroxyphenylalanine). Dopamine can then be made into norepinephrine and/or epinephrine.
Picture from Marty Hinz, MD: www.neuroassist.com
Serotonin and dopamine cannot cross the blood-brain-barrier, but amino acids can. Therefore, it is necessary to consume adequate amounts of 5-HTP (or L-tryptophan) and L-tyrosine (or L-dopa) in the diet or via supplementation to supply the brain with the building blocks it needs to properly manufacture serotonin and dopamine.
In regards to trichotillomania and compulsive urges to pull, supplementation is necessary as it is impossible to consume adequate amounts of the necessary amino acids in the proper balance to optimize neurotransmitter function and eliminate the urges to pull.