SHANGHAI, CHINA - JUNE 30: (CHINA OUT) A young boy plays Sony's Playstation 2 video game system at the 2005 Shanghai Animation FairJune 30, 2005 in Shanghai, China. China has a population of 370 million children and young people, making up a huge audience for cartoons and animation. Currently, 90 percent of the market is dominated by foreign producers from Japan and the U.S., with the largest share going to Japan. Most domestic cartoons are criticized for being old-fashioned and lackluster due to little originality in story and characters, dryness of content and persistent educational flavor. (Photo by China Photos/Getty Images)

If you're struggling to lay down some house guidelines for video games, remember the first rule of red wine: While a little bit can be good, too much is a problem.

A new study out of Oxford University has found that children who play console or PC games for an hour or less per day tend to be more social and satisfied with life than kids who don't play any video games at all.

Hear that, parents? Your kids should get in a round of "Mario Kart" before they start homework.

But that's not to say you should let your kid play way into the night. In fact, if your child exceeds that rather strict hour-per-day threshold, the study found the positive effects suddenly vanish. There's no noticeable effect, positive or negative, for kids who play one to three hours of video games compared to kids who play none.

And once a child is spending three hours or more in front of their Nintendo, video games begin to take their toll. The researcher found children playing that much every day are more likely to be less happy than non-gamers, as well as more likely to have problems with hyperactivity, attention and relating to their peers.

Andrew Przybylski, the behavioral scientist behind the study, came to his conclusion after polling 4,899 British kids aged 10 to 15 about their emotional states and video-game habits. The study was published in the journal Pediatrics this month.

Just because video games and mood are linked doesn't mean that one causes the other. Tons of other factors could muddy the causation, like that fact that parents who are able to buy game consoles may be better-off. Plus, a child's social life with family and at school is much, much more important to her well-being than video games, Przybylski wrote in the study.

The scientific pendulum has been swinging back and forth on video games for decades. At first thought to make kids violent (they don't), video games have been found to be good for us in all sorts of ways: They improve eyesight, help dyslexic kids read and even relieve pain. The idea is that video games, like all games, help people socialize and stimulate their minds.

But like eggs, red wine, dark chocolate and nearly everything else found to have surprising health benefits, video games seems to be best only in moderation. Przybylski says he thinks the benefits of playing are washed out once the time spent on video games eats into kids' other activities, like schoolwork.

"A large share of time devoted to games may crowd out engagement in other enriching activities and risk exposure to content meant for mature audiences," he wrote in the study.