The team conducted a trial using a 3D game called Sparx, which allows players between 12 and 19 to choose an avatar to complete tasks.
They play in a world which is overrun by 'gnats' ('gloomy negative automatic thoughts').
The tests showed depression and anxiety were reduced by one third, with 44 percent of teenagers recovering after completing at least four out of the seven game modules, in comparison to the 26 percent who recovered in usual care.
The programme was developed for teenagers who are reluctant to seek help for mental health issues, reports the British Medical Journal website.
Scientists said: "They suggest that it is a potential alternative to usual care and could be used to address unmet demand for treatment."
>Video game rock medley, Mario, Zelda, Halo, more - Watch Video
> Depressed cat stars in French art house film Henri 2, Paw de Deux