It's a hotly-debated topic online. A 2018 study of adults aged 18 to 36 in the United States and Spain showed that 73 and 77% of respondents, respectively, believed that viewing sexually explicit material in a relationship is not cheating. On the other side of the argument you have guys like Dr. Phil, whose website features this strongly-worded article about why porn shouldn't be allowed in relationships at all.

So is it okay to watch porn if you're in a relationship? We checked in with sex therapist Ian Kerner , PhD, LMFT, to find out how porn and relationships can fit together.

Is watching porn cheating?

Kerner told Men's Health that he does not believe that watching porn while in a relationship is cheating.

"I think its important to be having relational sex, and to make sure that youre present and energetic for relational sex, but I think that we also have a relationship with our own sexuality and I dont think that the two are mutually exclusive," he said. "I think its important to be able to masturbate in a relationship and choose how you want to get aroused."

When does watching porn in a relationship turn into something unhealthy?

Kerner said that it is possible to cross a line. Say your partner asks you not to masturbate to porn because they equate it with infidelity, and you agree in an effort to please them. If you then went ahead and watched porn, "Well, then, that would be cheating," Kerner says.

"If theyve made a promise or a commitment around not using porn and then they do use porn without telling their partner, then that could be considered a form of cheating," he explains.

What if two partners disagree about watching porn?

As with a lot of aspects in relationships, you'll have to settle on a middle ground when it comes to porn.

"In any relationship there are many, many things that you have to compromise and collaborate on, so its possible that youll have disagreements around aspects of sexuality that also require compromise and collaboration," he says. "If one person really doesnt enjoy porn and doesnt think theres a place for it in the relationship and the other person enjoys it, its important that they figure out how to collaborate and compromise."

That compromise could include watching porn together or setting aside times that either or both of you is allowed to watch porn on your own-it's up to you to communicate honestly and reach an agreement that makes both of you comfortable.

Should somebody feel threatened if their partner is watching porn that features people that dont look like them, or porn that features acts that they would never do in real life?

The short answer: no.

Kerner explained that the fantasy of porn differs from reality, and it doesn't mean that your partner wants to do exactly the same acts that are in the scene that they're watching. It's also important for your partner to have "the space to be able to fantasize," Kerner says.

But Kerner also realizes that it's normal to have questions about your partner's porn preferences, and he suggests talking to them if you feel uneasy.

"That doesnt mean that somebody cant be threatened by porn or wonder, 'I have no boobs and it seems like youre really into big boob porn, how should I interpret that?'" he says. "Well then, thats a conversation to have with your partner. Its important to bring your vulnerability to your partner."