My older brother out of no where is locked up in his room and sleeps 24 hours a day.?

My dad tried to talk to him but he is not talking to anybody. He installed a lock in his room and now his room is locked up all day and he just sleeps. He was always working and always playing basketball all his life. He stopped playing basketball and he quit his job. My mom said that its a drinking problem but he always had the drinking problem for few years but he still worked and always played basketball. I have friends that drink but they wake up in the morning and go to work or do something. Why would my brother install a lock in his room and sleep all day out of no where and wont talk to anybody.