Programmers that drink (hard) are like cooks blunting their knives. I knew a couple in my 20´s that went down this route, they are not programming today. The brain is a complex piece of machinery and damage that you do to it when you are young will come back to haunt you later in life, when the aging of the brain removes some of the reserves. It is really hard to see people that were whip smart lose their faculties, especially if they had a hand in the change themselves.