In the new trailer for the upcoming film Thanks for Sharing, actress Gwyneth Paltrow saunters across the screen in a lace lingerie set that is sure to keep viewers' eyes locked on her. But the film, which is about a recovering sex addict, revives a longtime debate: is sex addiction a disease or an excuse for guilty cheaters?

Set for release later this year, the movie follows Paltrow as she attempts to have a relationship with a recovering sex addict played by Mark Ruffalo. Time Robbins, Josh Gad, and singer Pink also star as struggling sex addicts. The film seems like it's going to be a lighthearted romantic comedy, but for many, sex addiction is no laughing matter. Relationships, marriages, and whole families have been destroyed by sex addiction. While some believe it is just a passing trend, a good number of experts say that compulsive sexual behavior is an actual disorder.

According to Mayo Clinic, compulsive sexual behavior occurs when one has obsessive sexual thoughts that interfere with their health, job, relationships, and general well-being. Sexual compulsions are progressive, meaning they usually begin with a normally enjoyable sexual experience that becomes an obsession.

Doctors are stumped as to what, precisely, causes compulsive sexual behavior, but it has been associated with a number of mostly neurological causes. Some of the causes may include an imbalance in serotonin and dopamine levels, variations in the levels of the sex hormone androgen, and brain conditions like multiple sclerosis, epilepsy, or dementia. People with substance abuse problems, mood disorders, and histories of physical or sexual abuse are at a higher risk for engaging in compulsive sexual behavior.

Treatment for sex addiction can involve any combination of psychotherapy, medication, and self-help groups. One popular group, Sex Addicts Anonymous (SAA), is "a fellowship for men and women who share their experience, strength and hope with each other so they may overcome their sexual addiction." SAA has a 12-step program to help sex addicts beat their addiction and offers group meetings for people to share their triumphs and failures.

But not all cheaters are sex addicts, so how do you tell?

"The term sex addict is very popular in the media, but it isn't well accepted within psychiatry," Eli Coleman, a psychologist at the University of Minnesota Medical School in Minneapolis, told US News & World Report. "There's a lot of debate about what really constitutes hypersexuality, and we have no clearly defined and agreed upon criteria for this."

The difference between cheating and sex addiction lies in one main thing: compulsion. If one cheats for a reason (i.e. their partner isn't giving them enough attention), then they're likely just a cheater. However, if someone has a prolonged, repetitive issue with engaging in destructive sexual behavior and can't help obsessing over compulsions, then it is more likely that he or she has a problem. Those with sexual compulsions "constantly think about and plan for how they're going to engage in some sexual activity," said Coleman.

"Every marriage has fights, troubles, broken promises, and couples can learn skills to do better," he said. "But when there really is some underlying mental disorder, we have to be careful not to minimize it and to get to its root cause."

It will be interesting to see if the addicts in the film mirror the behaviors of actual people who struggle with compulsive sexual behaviors or cater to what doctors see as a sensationalized, overdiagnosed image of the disorder.

Thanks for Sharing is set to open in theaters on September 20.