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The Sex Ratio of Full and Half Siblings of People Diagnosed with an Autism Spectrum Disorder: A Danish Nationwide Register Study

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Abstract

In the extreme male brain theory of autism sex steroid hormones are hypothesized to influence brain development and to mediate sex differences in developmental psychopathology. Within this scope we examined the sex ratio (proportion of males) in siblings of individuals diagnosed with autism spectrum disorders (ASD). We did a nationwide, register based cohort study of the sex ratio in 17,380 siblings of the 10,297 patients diagnosed with ASD at age 17 years and younger and registered in the nationwide Danish Psychiatric Central Register between 1994 and 2012. Among the 17,380 siblings 8,828 were males and 8,552 females. This yields a sex ratio of 0.508, which is not different from the Danish live birth sex ratio of 0.513 during the relevant years (P = 0.18). Overall, our findings provide no support for the hypothesis that there are relatively more males among the siblings of people with ASD. Accordingly, our results do not give support to the extreme male brain theory of autism.

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Acknowledgments

We are grateful to Mrs. C. Hermansens Foundation for financial support.

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Authors and Affiliations

  1. Child and Adolescent Psychiatry Centre, Bispebjerg University Hospital, 2400, Copenhagen, Denmark

    Svend Erik Mouridsen

  2. Hødersvej 5, Roskilde, Denmark

    Bente Rich

  3. Child and Adolescent Psychiatry Centre, Glostrup University Hospital, Glostrup, Denmark

    Torben Isager

Authors
  1. Svend Erik Mouridsen
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  2. Bente Rich
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  3. Torben Isager
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Correspondence to Svend Erik Mouridsen.

Additional information

Bente Rich Formerly associated with International Rehabilitation Council for Torture Victims, Copenhagen, Denmark.

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Mouridsen, S.E., Rich, B. & Isager, T. The Sex Ratio of Full and Half Siblings of People Diagnosed with an Autism Spectrum Disorder: A Danish Nationwide Register Study. Child Psychiatry Hum Dev 45, 493–499 (2014). https://doi.org/10.1007/s10578-013-0419-1

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