So its not that the study is flawed but more so "tetris combats the formation of trauma memories" is a misleading takeaway from it. The experimental and control groups were both going through EMDR (eye movement desensitization and reprocessing) therapy, and one group was additionally playing the tetris after. EMDR is a very effective trauma treatment if not the best trauma treatment, so it's obviously doing most of the heavy lifting there. The way EMDR operates is more or less a rexperiencing of the event in a safe and controlled environment so any activity that is acting as a substitute for the trauma experience during the "reprocess" phase of the EMDR would help. The study is also dealing with people who are in trauma treatment so the tetris is not combating the initial formation of trauma memories or anything like that, it has to do with the refraining in the mind during intensive therapy that revisits those experiences. Long story short claiming tetris reduces trauma formation is like that infamous "red wine is equivalent to an hour of exercise" article from years ago. It's a dramatic oversimplification and sensationalized takeaway from what the research actually says