I went through a phase of alcoholism. For me it was a comfort, something to deal with depression and the fact that my life was going nowhere at the time.
It took a little while for me to stop seeing it as an escape from reality and start enjoying a good drink, but I got there in the end, and it wasn't too difficult either. I'd say it wasn't strictly a choice (I felt driven to do something to make myself feel less terrible, and alcohol was the only way I knew how) but nor was it entirely involuntary (I knew exactly what I was doing, and I did it anyway).