According to an Oxford University study, playing Tetris immediately after a traumatic event can help reduce flashbacks, as it interferes with the way that such memories are solidified.
http://news.bbc.co.uk/2/hi/health/7813637.stmI hope their next study researches a cure for the Tetris Effect (where your brain unconsciously creates in-game puzzles to solve when you're not playing), or at least prevents "treated" victims from being disproportionately traumatized the next time they see a Z-shaped block.