Cowen P J, Parry-Billings M, Newsholme E A
University Department of Psychiatry, Littlemore Hospital, Oxford, U.K.
J Affect Disord. 1989 Jan-Feb;16(1):27-31. doi: 10.1016/0165-0327(89)90051-7.
Total plasma tryptophan was significantly lower in 12 depressed patients than in 12 normal controls. The ratio of total tryptophan to neutral amino acids was also decreased in the depressed patients suggesting that tryptophan availability to the brain might be reduced. There was no correlation between basal tryptophan concentrations in the depressed subjects and the subsequent neuroendocrine response to intravenous tryptophan.
