I agree with masses so far posted re reasons why drink heavily for periods, ( I did for 10 years too, like Krex), or get stuck to habits good and bad etc. Interesting about link between SMD/sensory integration disorders, esp the defensive type of which I have several, and substance abuse.
Food allergy-addictions too, wheat, dairy, sugar, etc, have profoundly influenced my life.
But am wondering about one which has not been mentioned. I think that my use of language is like an addiction. It consumes/drives and perhaps limits me in similar ways to an addiction. Aspergers are supposed to be particularly pernickety about grammar, spelling, correcting language errors, taking language very seriously, truth, etc, and often precocious readers, talkers/monologuers.
In the past I have found myself reading cereal packets, and I used to think that I was addicted to reading, which I am. But now think that I am addicted to the whole virtual reality structure called language. I love playing in it. Can not drag myself way from it. Much prefer it to most other activities, and most of my life have only been able to connect with people as addicted as me, which as can imagine has not been very good for my sex life!
I simply can not stop using it.