Social networking sites may be harmful to your health, an expert claims.

Dr. Aric Sigman says Web sites - such as Facebook and Myspace - are meant to easily connect people, strengthening and broadening social networks, but have had an adverse affect because they reduce levels of face-to-face contact.

Evidence suggests that the biological effects of minimal face-to-face social interaction could alter the way genes work, upset immune response, hormone levels, the function of arteries, and influence mental performance, reported the BBC News.

Dr. Sigman warns that this could increase the risk of serious health problems: cancer, strokes, heart disease, and dementia.

With the advent of these social networking Web sites the American Psychiatric Association is starting to recognize Internet addiction as a real affliction.

"It can really get addicting," Adriana Manago, a UCLA graduate student in psychology, told reporters for CBS News. "You start to want to stalk people. You kind of follow their every move. People who normally wouldn't be stalkers might even find themselves kind of following people online."

According to Dr. Sigman, there is research that suggests that face-to-face human interaction has steadily dropped since 1987.

Along with the health risks of social networking sites, Dr. Sigman argues that people are losing the ability to read body language and interact physically with other human beings.

As social networking in the digital realm continues to expand, human interaction continues to evolve with technology.

"Friends are kind of scattered all around the country," says UCLA graduate student Chris Beitel, as reported by CBS News. "So it's just kind of nice to be able to keep in touch with people."