A novel experiment conducted by Carnegie Mellon University Professor George Loewenstein and colleagues may explain why people try a drug, such as heroin, for the first time despite ample evidence that it is addictive. The results of the study, which are being published in the Journal of Health Economics, reveal that even longtime addicts underestimate the influence that drug cravings have over their behavior.

Almost all drugs produce a craving in their users. Loewenstein and his colleagues hypothesized that people experiment with drugs that they know are addictive in part because they can't appreciate the intensity of drug cravings, and thus underestimate the likelihood that they will become addicted. Because they can't imagine what it would be like to experience a craving, people also discount the possibility that they will do terrible things in order to satisfy that craving, such as commit crimes or abandon their children.

The researchers confirmed their hypothesis in a study that involved 13 heroin addicts being treated with the maintenance drug buprenorphine (BUP). During the eight weeks of the study, participants were repeatedly asked to choose between varying amounts of money or an extra dose of BUP, both when they were craving the drug and when they were not. The major finding was that addicts valued an extra dose of BUP about twice as much when they were craving it (right before receiving their normal dose of the drug) than when they were currently satiated (minutes after receiving the BUP) — even when they knew they would not receive the extra dose until five days later.

"If addicts can't appreciate the intensity of craving when they aren't currently experiencing it, as these results suggest, it seems unlikely that those who have never experienced a craving could predict its motivational force," said Loewenstein, the Herbert A. Simon Professor of Economics and Psychology. The study was co-authored by Gary J. Badger of the Biometry Facility at the University of Vermont College of Medicine; Warren K. Bickel of the Department of Psychiatry at the University of Arkansas; Louis A. Giordano of the Department of Psychiatry at Duke University; and Eric A. Jacobs of the Department of Psychology at Southern Illinois University.

The participants were shown 12 dollar amounts (ranging from $0 to $100) and for each amount specified whether they would prefer to receive the money or an additional 24-hour maintenance dose of BUP. They were told that one of their choices would be selected at random to count. Half the time, the addicts made their decision when their craving was highest — right before they received their normal dose. The other half of the time, they made the decision after they had received their normal treatment. In addition, half the time the subjects made a choice that would go into effect later that same day, and half the time they made a choice that they would not receive until five days later. Assuming addicts could appreciate how intense their desire for a drug would be, their future craving for it logically should not have been affected by whether or not they had just received treatment.

But this was not the case. The median minimum dollar amount preferred to an extra dose of BUP was greater when subjects were drug-deprived, whether the dose or money was to be delivered immediately or after five days, as compared to when they were satiated. When subjects were drug-deprived, they valued an extra dose five days later at $60, but valued the same dose at only $35 when they were not deprived.

These results not only offer insights into why people use drugs they know could be addictive, but could also help explain why it is so difficult for addicts to quit, according to Bickel.

"Individuals who are in treatment may think that they will be OK out of treatment. However, if they underestimate the power of drugs, they may be surprised that they relapse," Bickel said. "Similarly, adolescents may think that they can try drugs without ill consequence. But they may underestimate how powerful a drug is and therefore expose themselves to the drug."

To prevent recovering addicts from relapsing, they must be taught to anticipate, recognize and cope with situations in which they will be tempted to use drugs, Loewenstein said.

"People generally decide to go on a diet right after eating a satisfying meal; to start saving right after splurging; and to quit drugs, such as cigarettes, right after smoking one. But all of these plans tend to be unrealistic because they are made when people aren't in a craving state and, as our results show, can't predict what it will be like once they start craving again," Loewenstein said.

This article has been adapted from a news release issued by Carnegie-Mellon University