The indoleamine hypothesis of depression: an overview and pilot study

This paper reviews the evidence for a specific indoleamine deficiency in depression and the attempts to correct this suspected deficiency with serotonin precursors. It also presents the clinical and biochemical data on six patients with depression treated with L-5-HTP in a nonrandom, double-blind protocol. The oral administration of L5-HTP was associated with a rise in CSF5-HIAA, but only two of six patients studied had any decrease in depression ratings. 5-HTP was also shown to decrease urinary excretion of 17 hydroxycorticosteroids in twodepressed patients and three normal controls suggesting an interrelationship between serotonin metabolism and the pituitary adrenal system. This leads to the suggestion that in a postulated subgroup of depressed patients with pituitary adrenal hyperactivity and evidence of serotonin deficiency, L5-HTP deserves a further trial as an experimental treatment.