FRIDAY, Oct. 19, 2001 (HealthDayNews) -- You can wear the nicotine patch, attend Alcoholics Anonymous meetings faithfully, or avoid the old hang-outs where you once did drugs. But when it comes to kicking an addiction, your brain may be working against you.
A new study shows that drug use sensitizes the brain so that certain smells, sights or situations -- an ashtray, the sound of ice cubes tinkling in a glass, passing an alley where you used to shoot up -- can unleash powerful cravings, even years after you've stopped using.
But the research is no reason to give up trying to quit, said Kent C. Berridge, a psychology professor at the University of Michigan and co-author of the study. "Sensitized people can develop strategies to not give into it," Berridge added. "But if they have been sensitized, they are still exposed and vulnerable to those cravings."
The study appears in the October issue of the Journal of Neurosciences.
Previous research has shown that drug use causes anatomical changes in certain neural systems of the brain, Berridge said. There is also plenty of anecdotal evidence that ex-smokers, alcoholics and drug addicts who successfully quit can be plagued by cravings for years.
"It's a well-known phenomenon," said Dr. Roger Weiss, head of the American Academy of Addiction Psychiatry's research section. "People in early recovery of substance abuse need to be aware they are vulnerable to these cravings. The urges they experience are correlated with real brain changes and are not fully in their control."
Berridge said his study is among the first to uncover the psychological causes of the cravings.
Earlier research suggested several explanations for what Berridge calls "cue-triggered" cravings. One possiblity is that the cues trigger withdrawal symptoms. Another is that they trigger slight feelings of pleasure.
But Berridge said his study shows neither of those explanations is true. In fact, the cues trigger a neural system of the brain that causes excessive "wanting" of the drug.
Berridge and his researchers trained rats to press a lever to get a reward of sugar pellets. They also taught the rats to associate a 30-second tone with getting the sugar pellets, without needing to press the lever.
Then they sensitized the brains of one group of rats by injecting them with amphetamine. Another group of rats was injected with a saline solution.
The researchers waited 10 to 14 days to make sure the rats were drug-free. Then they redid the experiment using the sugar pellets and the tone.
This time, they found, the tonal cue sent the sensitized rats into a frenzy. They pressed the lever 200 percent more than the rats that had received only a saline solution.
Researchers also did the experiment with rats that were given tiny, painless injections of amphetamine directly into their brains. When they heard the tonal cue, those rats also went into a frenzy.
"Drug use is known to sensitize certain neural systems within the brain, causing changes that are relatively permanent," Berridge said. "This study shows the brain is vulnerable to cues that trigger irrational 'wanting,' even after a long period of remaining drug-free."
Researchers do not know how long a rat brain -- or a human brain, for that matter -- stays sensitized. It's probable that individual human brains have different levels of susceptibility to sensitization, Berridge said.
"It could last for months, years or a lifetime," he added.
Available treatments do not deal with these cue-driven cravings. The nicotine patch, for example, can help alleviate withdrawal symptoms, but it won't help control cue-triggered cravings.
What To Do: For information about treatments for drug and alcohol addiction and where to get help, visit the National Clearinghouse for Alcohol and Drug Information or the National Institute on Drug Abuse.
