People who want to break a bad drug habit may have to do more than avoid the sights and sounds that remind them of their addiction.
For years, researchers have known that external cues affect addiction by building up drug tolerance, which makes people need more and more of a drug to obtain the same effect.
However, internal cues are also at work, says a new study in the July issue of the Journal of Experimental Psychology: Animal Behavior Processes. These early, internal cues prime the body to react as if the drug effect is imminent.
The finding points out that addiction may be a psychological phenomenon, not just a physiological one. In turn, that could help those in treatment programmes to kick illegal drug use, as well as help doctors prescribe potent painkillers more safely.
"The important new finding is that part of the stimuli that elicits this learned response (to need more and more drug) comes from early drug effects," says study author Shepard Siegel, a professor of psychology at McMaster University in Hamilton, Ontario. These internal cues, he says, are as important as external ones.
In the study, Siegel and his colleagues gave rats infusions of morphine over several days, so the animals developed tolerance to the pain-relieving effects. It takes a few minutes after infusion for the peak effect of a drug to occur.
The researchers hypothesized that every administration would pair the early effects of the drug with the peak effect, and the animals would begin to associate the early effect with the later effect.
Next, they gave the animals a very small dose, about 10 percent of what they had been getting.
Expecting larger dose
A dose that small usually has no effect, especially after animals are used to a larger one. However, these animals responded as if a large dose was coming.
"The finding clearly shows that internal cues can be associated with addiction to a drug," Siegel says. "The finding should have an effect on cue exposure therapy. Cue exposure therapy is a form of desensitization. It's used for cigarette, drug and alcohol [cessation]."
Traditionally, therapists pay attention to external cues, such as a picture of a syringe. Now, the research suggests they should also pay attention to internal cues.
The research may also explain why relapses to a drug habit can be possible even when a person is exposed to a small dose, Siegel says. For instance, a recovering alcoholic may be vulnerable to a single drink because the body responds to the drug onset cue with a full-blown craving, as if a large dose is coming, and binges.
Siegel suggests desensitization therapy should include small doses to better replicate how the body responds to stimuli.
Role of learning
The new research finding builds on a body of research on the role of learning in drug tolerance, says Mark E. Bouton, a professor of psychology at the University of Vermont and editor of the journal, which is published by the American Psychological Association.
Besides helping administrators of drug-cessation programs and prescribing physicians, the research could help those fighting drug addiction because it shows there are many cues that can stimulate the urge to take drugs, Bouton says.
"Feeling the urge is not a sign of personal weakness," he adds. "Becoming aware of the cues that might be stimulating the urge can only help."
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