Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Aggressive Behaviour, Mental Sub-normality and the XYY Male


IT is well known that 1 per cent of males in institutions for the mentally sub-normal are chromatin-positive and that the majority of these have an XXY sex chromosome constitution1. In 1963 Forssman and Hambert2 reported on a survey of the nuclear sex of 760 male patients in three Swedish institutions for criminal and ‘hard-to-manage’ males of sub-normal intelligence. They found 2 per cent to be chromatin positive, but the chromosome constitution of these patients was not reported. Casey (personal communication) surveyed 942 males in two comparable institutions in England, and found 2.2 per cent of them to be chromatin-positive. He also studied the chromosomes of these 21 chromatin-positive males and found 7 to have either an XXYY sex chromosome constitution or to be mosaics in which the XXYY cells formed the major cell line. This finding of a third of the chromatin-positive males to have an XXYY cell line contrasted sharply with that of Maclean and his colleagues1, who studied 2,607 ordinary mentally sub-normal males, and found only 2 of the 28 chromatin-positive patients to have an XXYY constitution. This contrast led us to wonder whether an extra Y chromosome predisposes its carriers to unusually aggressive behaviour. We decided that if this were the case, then we might expect an increased frequency of XYY males among those of a violent nature. The purpose of this communication is to report our findings in a survey of mentally sub-normal male patients with dangerous, violent or criminal propensities in an institution where they are treated under conditions of special security.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Similar content being viewed by others


  1. Maclean, N., Mitchell, J. M., Harnden, D. G., Williams, J., Jacobs, P. A., Buckton, K. E., Baikie, A. G., Court Brown, W. M., McBride, J. A., Strong, J. A., Close, H. G., and Jones, D. C., Lancet, i, 293 (1962).

  2. Forssman, H., and Hambert, G., Lancet, i, 1327 (1963).

  3. Hauschka, T. S., Hasson, J. E., Goldstein, M. N., Koepf, G. F., and Sandberg, A. A., Amer. J. Hum. Genet., 14, 22 (1962).

    CAS  PubMed  Google Scholar 

  4. Fraccaro, M., Glen Bott, M., Davies, P., and Schutt, W., Folia Hered. Path., 11, 211 (1962).

    CAS  Google Scholar 

  5. Sandberg, A. A., Ishihara, T., Crosswhite, L. H., and Koepf, G. F., New England J. Med., 268, 585 (1963).

    Article  CAS  Google Scholar 

  6. Court Brown, W. M., Harnden, D. G., Jacobs, P. A., Maclean, N., and Mantle, D. J., Privy Council, M.R.C. Special Report Series, No. 305, H.M.S.O. (1964).

  7. Townes, P. L., Ziegler, N. A., and Lenhard, L. W., Lancet, i, 1041 (1965).

  8. Maclean, N., Harnden, D. G., Court Brown, W. M., Bond, J., and Mantle, D. J., Lancet, i, 286 (1964).

Download references

Author information

Authors and Affiliations


Rights and permissions

Reprints and permissions

About this article

Cite this article

JACOBS, P., BRUNTON, M., MELVILLE, M. et al. Aggressive Behaviour, Mental Sub-normality and the XYY Male. Nature 208, 1351–1352 (1965).

Download citation

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing