Why did Edgar Allan Poe start drinking?

There is evidence that Poe took hard drinks quite often when he was 17. A fellow student at the University of Virginia states that Poe "would seize a full glass ... and send it home at a single gulp. This frequently used him up; but, if not, he rarely returned to the charge."See http://etext.virginia.edu/poe/alumnews/poe-all.html

After his wife died he suffered from depression and Alcoholism. Poe eventually died because of his drinking problem.