Rational Addiction Model of Drug Use

The rational addiction model was proposed by economists Kevin Murphy and Gary Becker. The essential element of this theory that differs from other theories and lay perspectives on addiction is that addicts choose to consume drugs (or engage in other addictive behaviors, such as watching television or overeating) because engaging in the behavior maximizes discounted utility. Addicts are assumed to have full knowledge of the consequences of the addictive behavior, but calculate that there is greater benefit to using the drug relative to not using the drug. Future negative consequences are assumed to be discounted (their utility is reduced because they are delayed), but the drug is used because the sum of all discounted utility still favors drug use over abstinence. Therefore, addicts recognize that using the drug will lead to greater future drug consumption and that drug use may have negative consequences on health, work, or family, but judge that utility from drug use nonetheless outweighs the discounted decrease in utility resulting from these negative consequences.

The theory differs from the behavioral economic perspective of time inconsistency or hyperbolic discounting. This framework holds that not only is future utility discounted, but it is discounted specifically in a hyperbolic fashion (as opposed to an exponential fashion that is assumed by traditional economic theory), which leads to preference reversals. For example, an addict may sincerely want to be a nonuser a month from now, but use drugs tonight. Hyperbolic discounting functions predict this type of preference reversal when the objectively less desirable activity (drug use) becomes immediately available (e.g., a friend stops by with drugs to share). In contrast to rational addiction theory, hyperbolic discounting holds that individuals can become enslaved to their own short-term desires, despite longing for change in the long run. This is consistent with the notion of addiction being an issue of self-control, which is common in the public understanding of addiction. Substantial behavioral evidence from both humans and animals support the concept of hyperbolic discounting and resulting preference reversals. Rational addiction has also received some empirical support, such as results showing that publicized future tax increases can decrease current cigarette consumption. Extensions of the rational model of drug use have incorporated hyperbolic discounting, as well as uncertainty, in the conceptual model.

The rational model of addiction and hyperbolic discounting model of addiction can lead to very [Page 680]different perspectives on drug policy. Assuming that addicts do not suffer from self-control problems, but instead are operating with full knowledge of consequences, the rational model of addiction is consistent with a more libertarian perspective in which the government need not play a role in protecting people from the harms of drugs use. Alternatively, assuming that drug addiction is a self-control issue in which individuals use drugs without knowledge of the consequences, including increased future consumption, the hyperbolic discounting model of addiction is consistent with a perspective in which the government may decrease harms to people by preventing use of addictive drugs.