Gaming addiction is real and I don't know how to help

My 15yo has been gaming 5-6 hours a day after school and on weekends. It's affecting his sleep, his grades dropped, and he gets ANGRY when we try to limit it. I've tried everything—negotiating, taking away the console, consequences. Nothing works. He just sneaks it in other ways. I'm genuinely worried this is bigger than typical teenage stuff. Has anyone dealt with something this severe or should we be looking into actual treatment?