Central tryptamine turnover in depression, schizophrenia, and anorexia: measurement of indoleacetic acid in cerebrospinal fluid.

There has been a continuing interest in the possible role of the trace amine tryptamine in the etiology of neuropsychiatric disorders. We have therefore examined cerebrospinal fluid (CSF) levels of indole-3-acetic acid (IAA), the major metabolite of tryptamine, in a large group of normals and in several patient populations. No differences in CSF IAA levels (ng/ml, mean +/- SEM) were observed between normals (4.39 +/- 0.37, n = 36), anorectics (4.40 +/- 0.42, n = 35), schizophrenics (4.06 +/- 0.05, n = 17), manics (4.32 +/- 0.63, n = 10), or depressives (5.23 +/- 0.49, n = 39). A significant elevation (p = 0.05) was found in the subgroup of retarded depressives (RDC) where levels of 5.90 +/- 0.80 (n = 19) were observed. An age effect (r = 0.39, p = 0.02, n = 36) was observed in normals; however IAA was not reduced to either height or weight. IAA tended to be higher (but not significantly) in females in all groups studied; this difference also was not significant when all diagnostic groups (except anorectics) were combined (female: 4.95 +/- 0.44, n = 45; male: 4.46 +/- 0.30, n = 66). In general, the results indicate that tryptamine turnover is not altered in the disorders studied. The functional significance of the slight elevation seen in retarded depressives is not clear.