Both physical and mental.
My son was a good honors student till he got involved in PS3 Modern Warefare games in 2008, playing w/ people all over the country. One of his partners went semi pro. They made youtube videos w/ strategies that were highly viewed.
The point is he got addicted, playing all the time, school suffered, Adrenalin rush made him not able to sleep. His sleep schedule is still messed up and he has symptoms of Tinnitus like rock musicians from the bomb burst in a head set w/ microphones. He struggles to focus as it added to his ADHD or caused it, as you get so much stimuli from everywhere.
He graduated in the bottom third of his HS class and flunked out of college in 18 months. Was not prepared for college at all. Has troubling being on time for work today.
Gaming destroyed the kid in 5 years. I know I could have been a better parent and threw it out the window, but that led to fights with wife and you give up after awhile and ended up divorced with this gaming issue as a contributing factor but not 100% of it.