Like it or not, it’s a sexy world. The media ensures that children and adolescents are exposed to sex earlier than ever; girls are going through puberty earlier; and, as always, many teenagers are having sex.

As parents, we all have our opinions about when and with whom our children should be sexually active. So when is that age? And when should you worry? (Keeping in mind that “always” is not a viable answer.)

It should come as no surprise that there is little consensus among cultures about young people and sex. Take, for instance, a study that compared American teens with their Dutch counterparts: In the Netherlands, where parents routinely allow their children to become sexually active when they feel ready and host their children’s partners for sleepovers, the rate of teen pregnancy is an eighth of that in the US. “That’s all well and good,” a more conservative American parent might retort, “but abstinence is still the only foolproof method of birth control, and I’d prefer if my child waited until marriage to have sex.”

So: Are there any rules?

Before puberty

First off, children are not sexual beings. If a prepubescent child displays “sexual” behaviors, like touching genitalia, they could be the result of normal curiosity about his or her body and the bodies of others. If the behaviors occur more than occasionally, on the other hand, or include overt attempts to mimic or perform sex acts, it might be something to worry about.

Kids are “curious, and that’s how they learn about the world,” says clinical psychologist Dr. Samantha Miller, “but they’re also wired to mimic.” Remember—kids aren’t born knowing what sex is; if they’re aping it, they’ve been exposed to it. The exposure might be to pornography, which could indicate neglect, notes Dr. Miller; or it could be exposure to actual sex, or even abuse. A child who acts out sexually doesn’t really understand the behaviors as sex, which is why, if reinforced, they can lead to an unhealthy relationship with sex, their bodies, and the bodies of others that may be very damaging emotionally later on.

After puberty

After puberty—whenever it happens—adolescents are sexual beings, with urges that are fundamentally human. So-called “normative” sexual behaviors vary by culture. The point, according to Dr. Miller, is that whether you want a child to wait until marriage to have sex or just until she thinks she’s “ready,” it’s up to you to pass on your values by talking to her early and often.

But whatever your personal or religious values are there are other reasons to worry that cut across cultural and societal considerations.

Related: Why You Should Have Frank Sex Talks With Teens

Signs of emotional trouble

First, some sorts of adolescent sexual activity are clear warning signs of underlying problems—if your son coerces or even forces others into sex, he’s not only going against societal norms. That behavior is one of the symptoms of conduct disorder, a serious but treatable psychiatric disorder. If you’re alarmed by your daughter’s promiscuity, sexually transmitted disease is just one thing to be worried about. Risky, reckless sexual activity is also symptomatic of the mania found in bipolar disorder, and also may indicate a history of sexual abuse. And of course sex brings with it real risks—of pregnancy, disease, etc.

Beyond that, you might worry if you think your child is having sex for the wrong reasons. Maybe she sees sex as a means to validation, to deal with low self-esteem, to seek attention. Or as a way of dominating other people. Sex shouldn’t be a tool—if a young person is using sex to try to get something else or deal with troubling feelings, her attitude about sex can become distorted, and lead to problems down the road.

Related: How to Help Your Daughter Have a Healthy Body Image

Not just when but why
“There are no set rules about when children should have intercourse,” says psychiatrist Dr. Alan Ravitz. “But there are probably good rules about why children should have intercourse. They shouldn’t be having sex because they want somebody to like them. They shouldn’t be having sex because they feel coerced into having sex.”

Attitudes like that threaten a wonderful thing, Dr. Ravitz continues. “Having a great sex life is a blessing.” So how do you protect your child and make sure he or she grows up to have a healthy sex life? “Supervise and give guidance,” suggests Dr. Ravitz.

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