When you think of a hard-core gamer, do you picture a teenage boy battling his friends in World of Warcraft?

Think again.

The average gamer, far from being a teen, is actually a 35-year-old man who is overweight, aggressive, introverted — and often depressed, according to a report out this week from the Centers for Disease Control and Prevention (CDC) (download PDF). The study also shows that when children and teenagers become game players, a trend toward physical inactivity and corresponding health problems extends -- and is exacerbated -- into adulthood.

"Among researchers, there is growing concern and uncertainty about the health consequences of video game playing," the CDC reported. "Given the ubiquity of video games -- industry estimates suggest that they are played in 65% of American households -- these concerns may be justified."

The study notes that half of gamers are between 18 and 49 years old, while 25% are 50 and older. The CDC also pointed out that of online gamers aged 8 to 34, nearly 12% showed multiple signs of addiction.

The study, based on a 2006 online survey of 552 people between the ages of 19 and 90 who were living in the Seattle-Tacoma area of Washington state, also shows differences between male and female gamers.

Men reported that gaming gives them a "reason to get together," while women said they are looking more for a diversion than social interaction. Despite the fact that men and women offered differing reasons for playing, they experienced several of the same health effects.

Jim McGregor, an analyst at In-Stat, noted that his concern isn't just with gaming but with social networks, as well.

"My issue is that it's not just gaming. It's social networking. It's the Web in general," said McGregor. "We've gained so much, but still it puts people in front of a computer screen for hours on end. It gives Americans just another reason to be fat, dumb and lazy."

According to the CDC, both male and female gamers were more likely to report that they were overweight and had more poor-mental-health days and were less socially outgoing than non-gamers. Women were more apt to report that they experienced depression and other general health issues than women who aren't gamers. Male gamers, for their part, were more likely to report being obese.

"One interpretation of these findings is that, among women, video-game playing may be a form of digital self-medication.... In short, they can literally take their minds off their worries while playing a video game." noted the CDC. "Among men, the association among sedentary behaviors, physical inactivity and overweight status observed in children and young adults may extend into adulthood."