Nicotine Plus Alcohol May Be Tough to Beat

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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 analyze things at different levels than you might be able to do in the human population -- it provides a stepping stone," Gould said.

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 Center'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.

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's it's more damaging than either alone."

More information

To find out more about addiction, head to the U.S. National Institute on Drug Abuse.