A novel study may provide an answer to a question that has puzzled drug abuse researchers for years -- namely, why someone would try a drug like heroin for the first time knowing that it is highly addictive.

Based on their findings, the researchers infer that people experiment with drugs that they know are addicting partly because they can't fully appreciate the intensity of drug cravings and therefore underestimate the odds that they will become addicted.

The study, published online in the Journal of Health Economics, shows that even longtime drug addicts underestimate the impact that drug cravings have on their behavior. Therefore, inexperienced drug users are likely to be even more oblivious.

The study involved 13 heroin addicts attempting to get clean with the help of the prescription medication buprenorphine, which quiets cravings and other withdrawal symptoms.

During the eight-week study, participants were repeatedly asked to choose between varying amounts of money ranging from $0 to $100 or an extra dose of buprenorphine. They were forced to make a decision both when they were craving buprenorphine and when they were not.

The researchers predicted and found that heroin addicts valued an extra dose of buprenorphine more highly when they were currently craving it (right before the next dose) than when they were not craving it (right after receiving buprenorphine) - even when they knew the next dose was 5 days off.

"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," Dr. George Loewenstein, a professor at Carnegie Mellon University in Pittsburgh who was involved in the study, said in a press release.

Addicts who are in treatment may think they will be okay out of treatment, added co-investigator Dr. Warren K. Bickel of the University of Arkansas. "However, if they underestimate the power of drugs, they may be surprised that they relapse."

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," Bickel said.

SOURCE: Journal of Health Economics, online January 16, 2007.