Sex Questionnaire Cohort 1
Study Code:SX
Sample:4904 twins
Start Date:Mar.1992
Status:Completed
Contact:Anjali Henders
More Info:QIMR only


While there is a vast psychosocial literature on human sexuality, little serious biological research has been done on the aetiology of human sexual orientation. In view of the current AIDS epidemic, this is of some interest. We have obtained a grant from the US National Institute of Mental Health to investigate sexuality and sexual attitudes in volunteers twins from the Australian NH&MRC Twin Registry. Twin pairs' responses remain anonymous. Completed questionnaires have been received from over 1800 male and 3000 female twins. Preliminary analysis suggests a modest genetic contribution to male, but not female declared homosexuality. However, much larger genetic contributions are estimated for a latent variable indicated by thoughts of same-sex orientation, and measures of childhood and adult gender conconformity.

All members of the Alcohol Cohort 1 and Alcohol Cohort 2 studies were sent a consent letter asking whether or not they would participate in a sex-related questionnaire. They were asked to return the bottom part of the consent letter with their reply.

All those twins who answered "yes" were then sent a questionnaire and a consent form in the same package. The consent form had a label with the twin's demographic details and ID but the questionnaire had no identifying information. Twins were asked to return both the questionnaire and the signed consent form but in separate envelopes. In this way we could not match questionnaires to individual twins but the returned consent forms acted as a good proxy for return of questionnaire.

Each questionnaire had space at the top for a 10 digit number. The twins were asked to consult with each other and agree on a 10 digit number which they would then each enter on the top of their questionnaires. In this way, questionnaires could not be related to individual twins but twin pairs could be matched up.

The questionnaire contained sections on:

  • Background Questions
  • Childhood and Adolescent Behaviour
  • Your Present Personality
  • Sexual Feelings and Behavior
  • Family Information
  • Handedness
  • Your Feelings about the Questionnaire