A Critical Review of Recent Biological Research on Human Sexual Orientation

Brian S. Mustanski*, Meredith L. Chivers, J. Michael Bailey

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

147 Scopus citations


This article provides a comprehensive review and critique of biological research on sexual orientation published over the last decade. We cover research investigating (a) the neurohormonal theory of sexual orientation (psychoneuroendocrinology, prenatal stress, cerebral asymmetry, neuroanatomy, otoacoustic emissions, anthropometrics), (b) genetic influences, (c) fraternal birth-order effects, and (d) a putative role for developmental instability. Despite inconsistent results across both studies and traits, some support for the neurohormonal theory is garnered, but mostly in men. Genetic research using family and twin methodologies has produced consistent evidence that genes influence sexual orientation, but molecular research has not yet produced compelling evidence for specific genes. Although it has been well established that older brothers increase the odds of homosexuality in men, the route by which this occurs has not been resolved. We conclude with an examination of the limitations of biological research on sexual orientation, including measurement issues (paper and pencil, cognitive, and psychophysiological), and lack of research on women.

Original languageEnglish (US)
Pages (from-to)89-140
Number of pages52
JournalAnnual Review of Sex Research
StatePublished - 2002


  • Birth order
  • Developmental instability
  • Genetic
  • Homosexuality
  • Hormones
  • Phallometry
  • Sexual orientation
  • Vaginometry

ASJC Scopus subject areas

  • Sociology and Political Science
  • Psychology(all)


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