Rachlin (author of The Science of Self-Control) proposes an excellent analysis of the relationships between rationality and addiction. One the one hand, addicts are rational utility-maximizer: they use substances they like. On the other hand, destroying your life with drug is clearly irrational. He suggest first to consider rationality as "overt behavioral patterns rather than as a smoothly operating logic mechanism in the head" or "as consistency in choice" (the economic notion of rationality). He conceives rationality as "a pattern of predicting your own future behavior and acting upon those predictions to maximize reinforcement in the long run." Addicts are irrational "to the extent that they fail to make such predictions and to take such actions. "
- Rachlin Howard, In what sense are addicts irrational?, Drug and Alcohol Dependence, Volume 90, Supplement 1, Behavioral and Economic Perspectives in Drug Abuse Research, September 2007, Pages S92-S99.