Platelet size, number, and serotonin content in blood of autistic, childhood schizophrenic, and normal children.

Platelet volumes were measured in 19 autistic, 26 normal, and 6 schizophrenic children with similar blood serotonin concentrations. The groups did not significantly differ in platelet volumes, nor did platelet volumes and blood serotonin concentrations correlate. These results do not support the hypothesis that the hyperserotoninemia in some autistics reflects increased platelet volume.