title: A twin study of sexual behavior in men.
abstract: The role of genetic and environmental influences on age of initiation of first sexual relations and engaging in sexual activity with multiple partners (10 or more partners in 1 year) was investigated in male twins (N = 6,744) from the Vietnam Era Twin Registry. Individual differences in both types of sexual behaviors were heritable, but only age of onset of sexual relations was significantly influenced by the environment shared by the twins. There was a moderate negative correlation between age of initiation of sexual relations and the multiple partners variable; initiating sexual relations earlier was associated with a higher probability of having multiple partners. The additive genetic influence on age of initiation also influenced the multiple partners variable. The substantial unique environmental influences on each variable were uncorrelated with each other. The data suggest that the observed association between age of initiation of sexual relations and having multiple partners is due to genetic influences common to both behaviors.
authors.affiliation: Department of Psychology, Boston University, Boston, Massachusetts 02215, USA. mlyons@bu.edu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lyons
authors.forename: Karestan C
authors.initials: KC
authors.lastname: Koenen
authors.forename: Francisco
authors.initials: F
authors.lastname: Buchting
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Meyer
authors.forename: Lindon
authors.initials: L
authors.lastname: Eaves
authors.forename: Rosemary
authors.initials: R
authors.lastname: Toomey
authors.forename: Seth A
authors.initials: SA
authors.lastname: Eisen
authors.forename: Jack
authors.initials: J
authors.lastname: Goldberg
authors.forename: Stephen V
authors.initials: SV
authors.lastname: Faraone
authors.forename: Rachel J
authors.initials: RJ
authors.lastname: Ban
authors.forename: Beth A
authors.initials: BA
authors.lastname: Jerskey
authors.forename: Ming T
authors.initials: MT
authors.lastname: Tsuang
mesh_terms: D000328:Adult; D000367:Age Factors; D003075:Coitus / Q000523:psychology; D018451:Homosexuality, Male / Q000235:genetics / Q000523:psychology* / Q000706:statistics & numerical data; D006801:Humans; D007398:Interpersonal Relations; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012042:Registries; D012747:Sexual Partners / Q000523:psychology; D014427:Twins; D014481:United States / Q000453:epidemiology