Researchers Explore Mental Health Benefits of Video Games on Washingtonpost.com introduces us to Gail Nichols, a 49 year-old Kansas woman who found video games helped fight symptoms of her depression and post-traumatic stress disorder. She discovered this through playing Bejeweled, which inspired PopCap games to start studying the mental health benefits from gaming, while also occasionally supplying Gail with new games to see if they had similar impact on her condition. This quote offers theories on why games may help with this from Carmen Russoniello, director of the psychophysiology lab and biofeedback clinic that conducted research on this at the behest of PopCap:

The researcher hypothesized that one reason for the apparent mental health benefits of video games is that many people in Western countries find it impossible to switch off; they are always alert and stressed out. When those Type A people try to relax, they get bored because they have come to require a certain level of stressful arousal. Playing certain video games, Russoniello said, offers just enough mental challenge to keep such people occupied while putting them into a state of relative mindlessness. That state appears to have salutary effects on stress and other mental problems.