Greenfield said he has worked with executives who lock themselves in the office half the day looking at porn. Reid has treated others who stay up all night viewing online porn and come in groggy to work.

Both Reid and Tomb said their clients find viewing pornography an especially tough habit to break. Reid said giving up porn can be as difficult as giving up heroin.

However, other experts say viewing pornography does not qualify as an addiction.

"It depends on what we mean by addiction," said Jeffrey Schaler, a former psychology professor at Johns Hopkins University who has studied compulsive pornography viewing and addiction. "If we mean some disorder or some chemical imbalance, there's no such thing as pornography addiction. If by addiction we mean something that people enjoy and use to cope, then yes, there's such a thing as addiction."

Schaler, author of the book "Addiction Is a Choice," said too many people, from alcoholics to self-described sexaholics, use addiction as an excuse for behavior they find inappropriate. With enough willpower, any addiction — from heroin use to compulsive pornography consumption — can be overcome, he said.

Other psychologists, such as the late Al Cooper of the San Jose Marital and Sexuality Center in Santa Clara, Calif., have said that while pornography viewing can reach the point of compulsion, it does not meet the criteria of other physical addictions.

"It's not something people can't control," Schaler said. "It's not like a seizure."

Depending on your morals, pornography addiction is either a vexing sin or an annoying waste of time. To conservative Christians, pornography has long been viewed as a gateway to baser sins, such as adultery and rape.

The recent cases of Paul Turner, who tried to poison his wife, and Louis Darrell Kinyon, who shot his boss, seem to support such religious fundamentalist theory.

"I think it's dangerous when we attribute a criminal act to pornography, and there's obviously other factors we're overlooking," Schaler said. "It's more complicated than that.

"There's no evidence to show pornography caused (Turner and Kinyon) to do these things. People say, 'Well, pornography obviously had something to do with it.' Look, there are tons of people who read pornography and don't kill people."

There is even some debate about whether pornography addiction escalates. Reid said he has clients who have been looking at the same kind of porn for years, while Tomb said most people hooked on porn seek increasingly explicit material.