Sounds like utterly bullcrap to me. The main problem with ADHD is that kids are feed with sugar, sugar, sugar and well more sugar. On top of that all other additives and factory made food that some people put on the table. I mean it's not killing the kids giving them pure water instead of a coke?
Anyway correctly used and not used as cheap baby-sitter, computers are great for kids. The best example is learning kids to read and spell. If you cut away the pen/paper and not force the kids to try to write the letters first but instead let them type the words, sounding etc directly on the computer, they break the reading code much faster. thats because the kids dont need to booth learn to write the letters and sound them at the same time. First understand the letters, then write them by hand.
All in all, learn to cook real food on the thing called "STOVE" at home, throw away crisps, candy, coke. Pure meat contains far more Proteins and good fat than a Pizza and tastes way much better. Dont let the kids play video-games unguarded every day. Send them off out in the woods, make them attend to sports or other social activities. Using the computers as baby sitters is just plain stupid.