doi:10.1111/j.1469-7610.2012.02610.x Commentary: Additional sex chromosomes 1083 et al. (2011) considered boys and girls separately and found that XXY and XYY boys had similar communication proﬁles, whereas XXX girls had less evidence of pragmatic impairments. Findings of autistic features in XYY males is of particular interest. When XYY was ﬁrst described in the 1960s there was intense media interest in the idea that these were ‘supermales’ with unusual levels of aggression and criminality. An early study by Witkin et al. (1976) put these ideas into per- spective. Witkin et al. capitalised on the excellent medical, military and criminal public records available in Denmark, as well as the willingness of a high proportion of the population to cooperate by providing DNA samples to the researchers. By restricting their study to tall men, they were able to identify 12 cases of XYY and 16 cases of XXY in a population of over 4,000 males. They conﬁrmed a higher rate of criminality among XYY males than either XY or XXY males, but noted that the crimes mostly involved property rather than aggressive assaults, and could at least partly be explained in terms of the lower IQ of XYY males relative to XY males. The ﬁndings on autistic features by Lee et al. (2012) cast the XYY phenotype in a new light, sug- gesting that a tendency to get in trouble with the law may be related to deﬁcits in social communi- cation and interpersonal skills, rather than unnat- ural levels of aggression. Difﬁcult ethical choices still surround the topic of supernumerary sex chromosomes. In many coun- tries, when an abnormal number of sex chromo- somes is identiﬁed on prenatal testing, the parents References Bishop, D.V.M., Jacobs, P.A., Lachlan, K., Wellesley, D., Barnicoat, A., Boyd, P.A., ... & Scerif, G. (2011). Autism, language and communication in children with sex chromo- some trisomies. Archives of Disease in Childhood, 96, 954– 959. Lee, N.R., Wallace, G.L., Adeyemi, E.I., Lopez, K.C., Blumen- thal, J.D., Clasen, L.S., & Giedd, J.N. (2012). Dosage effects of X and Y chromosomes on language and social functioning in children with supernumerary sex chromosome aneuploi- dies: Implications for idiopathic language impairment and autism spectrum disorders. Journal of Child Psychology and Psychiatry, 53, 1072–1081. are offered a termination of the pregnancy. The study by Lee et al. (2012) therefore has important clinical implications, as well as theoretical importance, be- cause parental choices can be inﬂuenced by what they are told about the likely outcome of the child. As the authors note, we must be cautious in interpret- ing ﬁndings based on cases where an unusual karyotype only comes to light when a child is inves- tigated for behaviour problems. Nevertheless, all re- cent studies have found evidence of an increase in autistic features in boys with XYY identiﬁed prena- tally, where ascertainment bias is unlikely to account for associations with developmental difﬁ- culties. It is, however, important to emphasise that although there is an increased risk of both structural language problems and autistic features in children with additional sex chromosomes, there is wide individual variation. Some children with trisomies do not have any difﬁculties, and only a minority merit a diagnosis of autistic disorder (Bishop et al., 2011; Ross et al., 2012). Acknowledgement This commentary article, invited by the Editors of JCPP, has not been externally peer reviewed, but has been through a process of editorial review. Correspondence to Dorothy Bishop, Department of Experimental Psychol- ogy, University of Oxford, South Parks Road, Oxford OX1 3UD, UK; Email: dorothy.bishop@psy.ox.ac.uk Leggett, V., Jacobs, P., Nation, K., Scerif, G., & Bishop, D.V.M. (2010). Neurocognitive outcomes of individuals with a sex chromosome trisomy: XXX, XYY, or XXY: A systematic review. Developmental Medicine and Child Neurology, 52, 119–129. Ross, J.L., Roeltgen, D.P., Kushner, H., Zinn, A.R., Reiss, A., Bardsley, M.Z., ... & Tartaglia, N. (2012). Behavioral and social phenotypes in boys with 47, XYY syndrome or 47, XXY Klinefelter syndrome. Pediatrics, 129, 769–778. Witkin, H.A., Mednick, S.A., Schulsinger, F., Bakkestrom, E., Christiansen,K.O.,Goodenough,D.R.,...&Stocking,M.(1976). Criminality in XYY and XXY men. Science, 193, 547–555. Accepted for publication: 27 July 2012 2012 The Authors. Journal of Child Psychology and Psychiatry 2012 Association for Child and Adolescent Mental Health.