New studies reveal that a learned compensatory response can trigger "drug tolerance," a physiological process central to addiction. Drug tolerance makes people need more and more drug to get the same effect, whether pain relief or a "high." It’s newly discovered psychological aspect -- in which a drug-predictive cue primes the body to react "as if" the drug effect is imminent -- might be used to treat addiction more effectively. In short, if drug tolerance can be learned, there is a chance it can be unlearned, reducing or eliminating the tolerance-related cravings and other withdrawal symptoms that can lead addicts to relapse.
The findings appear in the July issue of the Journal of Experimental Psychology: Animal Behavior Processes, which is published by the American Psychological Association (APA). This study used rats, but addiction researchers frequently generalize from rats to humans because "rats, like humans, can become dependent on addictive drugs, and display drug tolerance and drug withdrawal symptoms," says co-author Shepard Siegel, Ph.D., of McMaster University in Hamilton, Ontario.
Researchers had already shown that the drug tolerance of rats getting morphine infusions depended on the presence of environmental cues (sights or sounds paired with drugs). These external cues typically have been used because they are easily controlled by the experimenter. The new findings demonstrate there also are internal cues not controlled by the researchers -- the early bodily sensations that the drug itself surreptitiously provides.
In their July article, Siegel, with Marta Sokolowska, a graduate student at McMaster University, and Joseph A. Kim, Ph.D., of the University of California, San Francisco, explain how they built on these earlier findings to add a psychological layer to drug tolerance's already known physiological layer.
In the lab, the researchers first infused rats with morphine over several days, causing them to develop tolerance to the analgesic (pain-relieving) effect of the opiate....................
