Autistic disorder and the endogenous opioid system.

The elevated activity of brain opioids has been implicated in the pathogenesis of autistic disorder. Research on plasma and cerebrospinal fluid levels of endogenous opioids in subjects with autistic disorder has produced conflicting results. The author suggests that the level of brain opioid activity is a contributing but not the determining factor in the pathogenesis of autistic disorder. The author further suggests that the development of autistic disorder is related to the interaction between the endogenous opioid system and various neurotransmitter systems in the brain.