Urinary homovanillic acid levels of autistic children.

Anomalies in dopamine metabolism were investigated by assaying total homovanillic acid, and its free and conjugated fractions, in the urine of 34 autistic, 34 normal and 34 mentally retarded children. An increase in total homovanillic acid in autistic and retarded children is apparently due to an increase of free homovanillic acid in the autistic group and to an increase of conjugated homovanillic acid in the retarded group. Further research needs to be carried out into the central origin of homovanillic acid and to establish its relevance to autistic children.