Effects of L-dopa in autism

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A study was designed to determine if blood serotonin concentrations could be lowered in autistic children by the administration of L-dopa and, if so, to observe possible clinical or physiological changes. Following a 17-day placebo period, four hospitalized autistic boys (3, 4, 9, and 13 years of age) received L-dopa for 6 months. Results indicated a significant decrease of blood serotonin concentrations in the three youngest patients, a significant increase in platelet counts in the youngest patient, and a similar trend in others. Urinary excretion of 5HIAA decreased significantly in the 4-year-old patient and a similar trend was noted in others. No changes were observed in the clinical course of the disorder, the amount of motility disturbances (hand-flapping), percent of REM sleep time, or in measures of endocrine function (FSH and LH). Possible mechanisms by which L-dopa lowered blood serotonin concentrations, increased platelet counts, and yet failed to produce other changes are discussed.

This research was supported by grants from the Veteran's Administration Research Service; Public Health Research Grants HD 01-58 and AM 08775; National Institute of Health Grant RR-3 to the Health Sciences Computer Facility, UCLA; The National Institute of Child Health and Human Development Grant 04612 from the Mental Retardation Center, UCLA; and by the Department of Mental Hygiene, State of California.
The authors wish to express their appreciation to Dr. Joseph Beckerman, Miss Ann Catino, Dr. Gunnar Heuser, Dr. Charles Markham, Miss Gwen McAfee, Miss Terry Preston, Dr. J. Raymond, Mr. Martin B. Scharf, and Dr. Tjiauw-Ling Tan for their assistance and participation in this study.