The casual teen hookup culture is celebrated at Harvard, Yale and elsewhere on campuses with students still in their teens.

Yet a recent study by a Cornell University researcher finds that casual hookups for teens increases the risk of depression three-fold.

Teens who date and are sexually active are known to be at elevated risk for depression, but why those associations exist is poorly understood.

Now a new Cornell study has found that casual sexual “hookups” increased a teenager’s odds for clinical-level depression nearly threefold, whereas dating and sexual activity within a committed relationship had no significant impact. The effects held true for boys and girls, though younger teens (13-15 years old) who had so-called “nonromantic sex” faced substantially greater risks for depression. In contrast, dating alone was not linked to depressive symptoms, nor was sexual activity within a stable, committed relationship.

Researchers led by Jane Mendle, assistant professor of human development in Cornell’s College of Human Ecology, said the study provides evidence that “context is key” when trying to understand how teen relationships and sex affect their well-being. The research is published online in the Journal of Abnormal Psychology.

“Many historical and media perspectives have presented adolescent sexuality as an indicator of problematic or even socially deviant behavior,” Mendle said. “But this study and other recent findings are showing that’s not the case, and adolescent dating and sexuality can be viewed as normal developmental behavior.”

Using a novel behavioral genetics approach that compares siblings growing up in the same home, Mendle and her co-authors analyzed responses from 1,551 sibling pairs ages 13-18 from the National Longitudinal Study of Adolescent Health, a nationally representative sample of U.S. high school students initiated in the mid-1990s. Among other topics, teens answered questions about their mental health and dating and sexual history. Nearly two-thirds of the sample’s youth had dated, and two-thirds were virgins.

By comparing siblings in their study, the authors could control for family and environmental influences that might also raise one’s risk for depression.

“We designed the study to give us a purer way to isolate many of the factors that could be contributing to depression,” Mendle said. “It allows us to compare specific types of social activities — in this case, dating and romantic and nonromantic sex — to see their overall effect.”

The paper notes that not all the associations at play can be unraveled, however. For instance, some teens who have depressive symptoms or clinical depression may be more likely to engage in casual sexual behaviors.

Mendle, a licensed clinical psychologist who studies how such developmental processes as puberty and sexual maturation influence teens’ emotional growth, believes adolescent sexuality is important to study because it is closely tied to how well people transition into adulthood.

“One of the hallmarks of adolescence is the formation of romantic relationships, and we know that what happens in adolescence is strongly related to your psychological, physical and financial well-being for years to come,” Mendle said. “Findings like this can help shape the dialogue and public debate about how to best support teen sexual health, psychological development and other areas.”

The study co-authors include Sarah Moore, a Cornell graduate student in the field of human development; Joseph Ferrero, formerly a graduate student at the University of Oregon; and Paige Harden, assistant professor of psychology at the University of Texas.

The study was funded in part by Cornell.