PITTSBURGH, Feb. 12 People who try illegal drugs underestimate the influence drug cravings may have over their behavior, according to a U.S. study.George Loewenstein of Carnegie Mellon University 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.The researchers confirmed their hypothesis in a study that involved 13 heroin addicts being treated with the maintenance drug buprenorphine, or 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.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, says Loewenstein. The findings are published in the Journal of Health Economics.Copyright 2007 by UPI