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It's well known that "the success rate for stopping drinking is much lower if someone continues smoking," noted lead researcher Thomas J. Gould, a neuroscientist and associate professor of psychology at Temple University in Philadelphia. The concurrent use of "ethanol [alcohol] and nicotine can lead to very serious problems," he added.
Negative spiral
His team found that mice suffer deficits in their ability to learn and remember as they are withdrawing from nicotine. Furthermore, alcohol use appears to have negative effects on nicotine withdrawal. Interactions between the two addictions may generate a "negative spiral" of tolerance and dependence on both substances, Gould said.
That could explain why a smoker who walks into his favourite smoke-filled bar may feel like drinking. In the same situation, a social drinker who normally doesn't smoke may start craving a cigarette if they're having a drink, Gould said.
The mouse model's demonstration of the effects of withdrawal from chronic smoking also suggest an explanation of why light smokers may initially feel stimulated by nicotine but lose that stimulation as the habit continues, Gould said. When smoking becomes chronic, the initial stimulation is blocked and, instead, cognitive deficits begin to show up.
"So, it takes any of the positive effects and shifts the dose-response to the negative end quicker," Gould explained.
Cognitive deficits
Similarly, someone addicted to alcohol has "pretty strong memories of the first time they drank," Gould said. But because of the cognitive deficits created by alcohol abuse and their impact on new learning, alcoholics have a harder time remembering the adverse effects alcohol has now. These later memories aren't as "driving" as the fonder and stronger memory of that first drink, he believes.
The genetic make-up of mice and humans is 96 percent alike, so the results of these animal studies "gives you clues of where to look and allows you to analyse things at different levels than you might be able to do in the human population - it provides a stepping stone," Gould said.
Where tobacco, alcohol interact
The next step in his research will be to identify where in the brain tobacco and alcohol interact, he explained.
"If we can understand what changed and how it changed, then you can perhaps devise better interventions" for people, Gould said.
"There is a lot of clinical sense" behind Gould's findings, said Dr Rob Vorel, a psychiatric fellow at Columbia University Medical Centre’s division of substance abuse in New York City.
Vorel said there is a lot of interest in how cigarette smoking affects cognitive function and thinking. For example, when smokers stop smoking, they often find that they can't get any work done - and then start smoking again, so they can be more productive.
Why so many alcoholics smoke
Without having seen the study's data, Vorel said, "it sounds like they actually found a correlation between alcohol and nicotine at the mouse level. Nicotine and alcohol dependence are so common, and it [the study] may reveal some mechanisms that reveal why so many alcoholics smoke."
The limits of this type of animal study, Vorel added, are that the findings are "not more than predictions of ideas to test. From an intellectual level, it's an important step forward."
Barbara Flannery, a research psychologist for RTI International, a scientific institute in Baltimore, agreed.
"Certainly, this can translate to humans. It's harder to learn when you're addicted to alcohol," she said. "I think that multiple abuse dependence on various substances like nicotine and alcohol definitely has an additive effect in that it's more damaging than either alone." - (Carolyn Colwell/HealthDay News)
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