A Psychiatric Investigation of Triple-X Chromosome Females

Abstract

Among recent developments in human chromosome studies a triple-X state has been recognized in females in whom the chromosome number is 47, composed of 44 autosomes and 3 X chromosomes (Jacobs et al., 1959). Early surveys of nuclear sex have shown that the triple-X state is a not uncommon chromosomal anomaly. A survey of Edinburgh babies gave a frequency at birth of these abnormal females of 1.78/1,000 births (Court Brown, 1962) and by combining data of surveys from Edinburgh (Maclean et al., 1962), Glasgow (Fraser et al., 1960) and Baltimore (Johnston et al., 1961) the estimated frequency of the triple-X state in mental subnormality institutions is 4.51/1,000 in-patients.