Decreased plasma tryptophan levels in major depression
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P J Cowen1, M Parry-Billings, E A Newsholme
1University Department of Psychiatry, Littlemore Hospital, Oxford, U.K.
Journal of Affective Disorders
|January 1, 1989
Abstract:
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.