For high school girls, the reality of romance often feels less like Cinderella and more like Kill Bill. And while the emotional maturity level of your average high school boy definitely doesn't help, the pressure we put on girls to see relationships as cornerstones of their identities is the real culprit.

That's the conclusion of a new study from the University of New Mexico, which found that girls are more likely than boys to experience negative mental health effects when the reality of a given relationship doesn't match up with their expectations of it. "Romantic relationships are particularly important components of girls' identities and are, therefore, strongly related to how they feel about themselves – good or bad," the author of the study, Brian Soller, an assistant professor of sociology and a senior fellow of the Robert Wood Johnson Foundation Center for Health Policy at the University of New Mexico, said. "As a result, relationships that diverge from what girls envision for themselves are especially damaging to their emotional well-being."

Boys, Soller said, don't exhibit the same negative emotions because they don't identify themselves according to their relationships. They identify themselves by their interests – including sports and extracurricular activities. So when their romantic relationships aren't what they envisioned, it doesn't feel like as much like a personal failing.

The lesson of the study? Quit teaching girls to define themselves by their romantic relationships.

That teaching happens formally and informally. In many abstinence-based sex education programs, girls play games that include picking all the petals off a rose to symbolize the "fact" that they lose a fundamental part of themselves every time they have sex. At home in two-parent families, girls often see mom doing more of the emotional labor of childcare and partner-care than dad. We celebrate marriages as the most important day of a woman's life, expecting brides to spend thousands planning and executing perfect weddings – but it's much more rare to hear someone tell a groom that the wedding is his "big day," or hear a groom say he wants to look like a prince on his wedding day. Women still overwhelmingly take their husbands' surnames upon marriage, literally naming themselves according to their relationship. And even in the political realm, women routinely reference their roles as mothers and wives alternately to justify an opinion or to soften the threat of their own power – witness Michelle Obama calling herself the "mom in chief," or the legions of writers who cover issues around health and politics but identify as "mom bloggers."

There's nothing wrong with valuing the relationships in your life, romantic and not. For most of us, our relationships are at least one key to our happiness. But happiness is different from identity, and girls grow up not seeing relationships as potential value-adds to an already-rich life, but as the defining factor of that life. Of course they're devastated every time one goes sideways.

We also can't separate what we teach girls about relationships from what we teach them about sex. The study itself looked at expectations of physical intimacy – participants were given cards to indicate what physical acts they would like to see happen in their relationships (hand-holding, kissing, sex) and the order they wanted those acts to happen. A year later, they repeated the process, only this time indicating what actually happened in the relationship. Then, researchers evaluated their mental health, which was often poor.

American girls grow up in a culture where women are ornamental, and a very particular type of woman with a very particular type of body is used to represent sex itself in advertisements for everything from cars to web-hosting. But girls also hear that they are the gatekeepers to sex, that having sex too soon or with too many people will leave them damaged, and that men don't respect the women who sleep with them. Sex, girls learn, is a thing boys want and girls have, but the girls aren't supposed to give it up too easily – and that sex isn't about their own desires, anyway. Yet somehow, if girls just play by these contradictory rules – if they're pretty and sexy, but not sexual or slutty – their Disney-movie Prince Charming will just ride up.

For girls and women, that combination of relational identity and sexual schizophrenia is particularly toxic and soul-crushing. Policy-wise, there's a lot to be done: ending abstinence-only sex ed and finding more funding for a diversity of educational programs including art and music that can help all students forge individual identities and develop their talents would be a start. Outside of schools, policies allowing women to be equal players at work and in life would go a long way in shifting assumptions around female identity. These should include: paid leave for new parents so that moms don't have to choose between work and family and dads are expected to do both as well; wide access to both contraception and abortion with the understanding that women want to have sex for pleasure and not just to reproduce; and state-subsidized childcare so that parents aren't bearing the burden alone.

But profound social shifts are even more important than news laws. Some of those shifts, of course, will come along with more progressive social policies. But some we just have to take responsibility for ourselves, including adult women modelling healthy female self-identity apart from their relationships, and adult men embracing the importance of their relationships and displaying their capacity for caregiving. It also means praising our daughters more often for their talents, abilities and hard work, and not just for their helpfulness, beauty and behavior toward others. It means expecting our sons to be emotionally competent, generous and sensitive to how their actions impact the people around them.

There's no weakness in loving the people you love or in prioritizing your family and significant other. But there are dangers in a model of womanhood defined by sacrifice and folding yourself into others. We all want girls to develop positive self-esteem and feel a strong sense of self-worth. But it's awfully hard to do that in a society where, for girls and women, self-identity is relational and not about yourself at all.