Sex addiction is probably more common than most people believe and may affect up to nine million Americans, according to a report in Newsweek. Experts from the Society for the Advancement of Sexual Health estimate that three to five percent of the population have compulsive sexual behavior, also known as hypersexual disorder. About 90% of those with the disorder are middle-aged men, but it appears to be increasing among females, teenagers, and senior citizens. The number of sex therapists that provide treatment increased from 100 to 1500 in the past ten years. "It used to be 40- and 50-year-old men seeking treatment," said Tami VerHeist, vice president of the International Institute for Trauma and Addiction Professionals. "Today grandfathers are getting caught with pornography on their computers by their grandkids, and grandkids are sexting at 12." The usual explanation for the increases in the number of sex addicts is the increased availability of pornography. Newsweek is reporting that every day 40 million people visit the 4.2 million websites that offer free pornography on a 24\/7 basis. The theory is the more people watch pornography and send each other provocative images of themselves, the more they want the real thing. Whether sexual addiction is similar to drug and alcohol dependency and whether it causes changes in the chemistry of the brain is a controversial question. Many people in the therapeutic community, including Robert Weiss, founder of the Sexual Recovery Institute in Los Angeles, believe hypersexual disorder is a brain disease that should be considered a medical condition. "It's about chasing that emotional high: losing yourself in image after image, prostitute after prostitute, affair after affair," he said. "They end up losing relationships, getting diseases, and losing their jobs." Others believe there is no such thing as sex addiction, and that it is not an epidemic. Psychologist and author Dr. David Ley believes sex addiction is modern mythology. "The sex addiction concept is a belief system, not a diagnosis," he told Newsweek. "It is not a medically supported concept. The science is abysmal. The thing that drives me crazy is it that over the past year or two, they have started trying to use brain science to explain it. They are now talking about morphological changes that supposedly happen in the brain when somebody watches pornography or has too much sex." Several celebrities, including Tiger Woods and Charlie Sheen, are reputed to be sex addicts. There are many treatment programs available for the condition.