An interesting idea which does seem to make sense when you think about it!
Most people will have a device with them with access to similar games - maybe the NHS should start encouraging people to use them whilst waiting.
At the very least it would help to pass the time...
Tetris, or similar games, require a high degree of visual attention. The idea of the study is that these types of activities may lessen people's intrusive thoughts after a trauma, such as a car crash. This in turn might lower their risk of developing PTSD. It's important to point out that the treatment with Tetris was not intended to wipe out people's memories of the accident. They were still able to remember the accident when they voluntarily thought about it. The treatment is designed to reduce unwanted, intrusive and distressing memories which pop up when people are trying to do other things. The study authors say the computer game could act as a "cognitive vaccine" to help prevent psychological illness. There are many different types of trauma experience and this technique may not be appropriate for all of them.