Thirty-five males with double Y chromosome

Abstract

SYNOPSIS Thirty-five males with double Y chromosome were studied. Among the features observed in certain subgroups of these 35 were a more than average height, minor vertebral abnormalities, abnormal seminiferous epithelium, minor EEG abnormalities, and a mean intelligence level significantly below the expected. Fifteen of the 35 were found in institutions for criminals. The frequency of XYY males among 1,500 criminal males was 8·67 per 1,000 compared with 1·24 per 1,000 among 6,455 randomly selected males in the general population. Males with double Y chromosome tended to have more difficulties at school, to be more mentally immature, to be more impulsive than their siblings, and to have more difficulty in making relationships with others.