Michael Leahy, a recovering sex addict and founder of www.bravehearts.net, says he got into voyeurism as part of his 30-year pornography habit. Over time, online porn became boring, Leahy wrote in his 2008 book, “Porn Nation.” He started viewing “darker genres,” including Web sites with “hidden camera images of unsuspecting women.”

“Then one day, during a business trip,” he wrote, “I found myself in a hotel room looking out my window, and I spotted a woman in another room with the curtains slightly open.” Watching her undress was a captivating experience, and he soon found himself spending hours around windows, hoping to replicate the scene.

Leahy—who has been in recovery for more than 10 years—was troubled by his voyeurism, and knew he had “crossed a huge line.” But he blamed the women for “leaving the curtains open” and excused himself because he was “just looking through my window,” not “creeping around outside peeping into other people’s rooms.”

However, voyeurism is a federal offense and a local crime. Nonconsensual video recording or photographing of people in a state of undress in locations where they have a reasonable expectation of privacy is prohibited in every state and the District of Columbia, said Ilse Knecht of the National Center for Victims of Crimes.

Leahy’s path into voyeurism is quite common, said John O’Neill, a certified sex addiction therapist and director of addiction services at Menninger Clinic in Houston. It’s like other addictions, he said. People build a tolerance to certain stimuli, and seek something more, or something else, to reach the same excitement.

“For some people, the different voyeuristic types of pornography or the opportunity to spy on people, to look at somebody, is incredibly exciting,” said O’Neill. “It not only takes on a sexual connotation, it also takes on ‘I’m doing something wrong.’”

“Voyeurism generally does show up with male patients…and what makes it become such a big problem so fast is the use of the Internet,” said Susan O’Day, a therapist at the sexual recovery program at Sierra Tucson in Arizona.

Typically, a person with voyeurism will try to view many Internet sites at the same time, said O’Day. As he races between images and videos, “the mind goes into a state of hyperarousal.”

“It’s like crack. They don’t sleep and the images they’ve been looking at—many people report that those have been ‘burned’ into their brains, so that they have intrusive images later on. The worst part of it is that any sexual relationship with a human being, particularly a spouse, cannot compete with all that intensity,” said O’Day. “So very frequently, [men] lose their ability to function, sexually, in an intimate relationship.”

In fact, a husband’s sexual dysfunction is often “the tip-off to the wife that something’s really wrong.” If men really understood that pornography-related addictions, including voyeurism, often lead to an inability to form emotional, romantic bonds or perform sexually with a mate, O’Day added, “they might be more motivated to get some help with it.”