Tiger Woods is scheduled to break his months-long silence about the sex scandal that has plagued the world's most famous athlete. It's not clear how he will explain himself, though according to some reports Woods has been attending a private rehabilitation clinic in Mississippi that treats addictions — including sex addiction.

Infidelity is not uncommon among men (and women) all over the world. Plenty of people cheat on their spouses: according to one survey, 25 percent of men and 17 percent of women have been unfaithful. That, of course, doesn't make them sex addicts.

Woods's alleged actions — cheating on his wife with several women and/or visiting prostitutes—is not particularly unusual behavior, especially for a celebrity. Film stars and professional athletes have the money and power to indulge their illicit desires — as well as the ability to buy discretion. But when those desires spin out of control into divorce court (or, worse yet, failed endorsement deals), some seek professional help.

Addicted to Sex?

There's good reason to believe that people can be physically and psychologically addicted to specific substances (such as drugs). The idea that people can be addicted to specific behaviors (such as gambling) is also widely accepted.

But can a person be addicted to sex?

Some therapists — especially, of course, those who treat sex addictions — defend the diagnosis as valid, but many mental health professionals aren't so sure. For one thing, there are currently no universally agreed-upon tests or criteria that diagnose sex addiction.

"Sex addiction is one of those pop psychology diagnoses that has scant scientific support," Scott Lilienfeld, Associate Professor of Psychology at Emory University and co-author of "50 Great Myths of Popular Psychology," told LiveScience.

The problem, Lilienfeld explains, is that the label "sex addiction" involves circular reasoning.

"It's not at all clear whether the term explains, rather than merely describes, people's sexual behaviors," he said. "At this point, it seems to be the latter: when we hear that someone has a 'diagnosis' of sex addiction, we haven't really learned anything new. We've merely applied a label summarizing what we already knew—basically that the person has serious trouble containing his or her sexual impulses."

Creating the Diagnosis

Many in the psychological field who are skeptical that sex addiction is a disease point to a phenomenon called the "pathologizing the ordinary" — creating a category of mental disorder to redefine socially unacceptable behavior as a disease. The idea is that people have little or no control over diseases (unlike voluntary behaviors) so the patient has less responsibility for his or her actions.

If Woods claims to be suffering from a sex addiction, he can adopt the role of victim (or sufferer) instead of a perpetrator (or pervert).

Society does not classify diseases in a vacuum. Social norms change over time, and influence which behaviors and actions are considered abnormal. It happened with homosexuality, which up until 1973 was classified as a mental disorder by American Psychiatric Associate in their Diagnostic and Statistical Manual.

If everyone golfed like Tiger Woods, he wouldn't be unusual, and if everyone acted like him, there would be no diagnosis of sex addiction. Whether Woods takes full responsibility for his actions or suggests that he's suffering from a mental illness, one thing he's sure to say is, "I'm sorry."