







Genetic factors related to how sexually mature a girl thinks she is influence her sexual behavior, above and beyond her actual physical development, reports a new study.

The study, published in June in Developmental Psychology (Vol. 50:6), is the first to directly test the link between pubertal timing and involvement in specific sexual behaviors, disentangling the genetic and environmental influences shaping adolescent sexual timing and behavior, the authors say. Their findings indicate that unique genetic factors influencing how mature girls think they are predict their engagement in dating, romantic sex and casual sex, whereas genetic factors associated with the timing of puberty predict the age when girls first become sexually active.

“We’ve known for a long time that when kids go through puberty is strongly influenced by genetic factors, but there’s more to puberty than just biology,” says Jane Mendle, assistant professor of human development in Cornell’s College of Human Ecology and recipient of this year’s Young Investigator’s Award from the Society for Research on Adolescence.

“Dramatic social and environmental changes take place as kids transition into the new roles that come with sexual maturity; it turns out that how girls interpret and respond to these changes is also genetically influenced,” Mendle says.

“While environmental influences are extremely important in the dating and sexual outcomes we studied, we were surprised that genetic factors played such a large role,” Mendle adds.

“We suspect that genetically influenced traits such as sensation seeking and sociality could be at play in shaping how teens navigate the complex social environments surrounding puberty,” says Cornell graduate student Sarah Moore, who is first author on the study, “Pubertal Timing and Adolescent Sexual Behavior in Girls” with Mendle and K. Paige Harden from the University of Texas.

The researchers analyzed information from more than 900 female sibling pairs in a national longitudinal study of adolescent health and risk behavior. The pairs included identical twins, fraternal twins, half siblings, cousins and unrelated siblings, allowing the researchers to distinguish the effects of environment from heredity.

The team found that shared genetic influences on age of puberty and on how girls perceive their physical maturity were responsible for differences in the age at which girls became sexually active. Girls who matured earlier than their peers perceived earlier maturity and also initiated sex at an earlier age. Potentially, this is because genetic factors such as hormone levels influence age of menarche and also affect visible appearance and sexual desire, the authors say.

Genetic factors related only to girls’ perceived maturity, on the other hand, were responsible for their engagement in sexual behavior. Girls who perceived earlier maturity than their peers were more engaged in dating, romantic sex and nonromantic sex. Furthermore, the team found no association between girls’ involvement in specific sexual behaviors and genetic or environmental factors influencing the onset of puberty. In other words, pubertal timing itself is not a risk factor for casual sex as some prior research had suggested, say the authors.

“Our research shows that girls’ perceptions of their pubertal development are different from their actual pubertal development and drive different outcomes down the road,” Mendle concludes.

Karene Booker is an extension support specialist in the Department of Human Development.