Monoamines in autism: an update of neurochemical research on a pervasive developmental disorder.

Recent neurochemical studies of norepinephrine (NE), dopamine (DA), and serotonin (5HT) in autism are reviewed. Most studies of the catecholamines, their metabolites, and associated enzymes have not found differences between autistic and normal subjects. However, a robust increase in platelet 5HT has been well replicated and characterized. Studies on the possible causes of the increased platelet 5HT in autism suggest that an alteration in platelet physiology is the cause of the increase. Future directions for research on the platelet are discussed as are other potentially fruitful methods for examining monoamine functioning in autism.