Whole blood and urinary levels of serotonin (5-hydroxytryptamine; 5-HT
) and the derivative urinary 5-hydroxyindoleacetic acid (5-HIAA) were
measured in normal and autistic subjects. An association was tested be
tween autism and a marker coding for the 5-HT2A serotonergic receptor
gene. Significant group (high urinary 5-HT and low whole blood 5-HT in
autism) and age effects (urinary 5-HT decrease with age) were found.
Moreover, whole blood 5-HT levels were correlated with clinical state.
No differences in allele and genotype frequencies for the 5-HT2A rece
ptor marker were found in this autistic population compared with age-m
atched healthy students.