June 2011

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How Secondhand Smoke Affects the Brain

Even if you don’t smoke, a new study shows, secondhand smoke affects your brain much as it does a smoker’s. It’s one more reason to steer clear of secondhand smoke in cars and other enclosed spaces.

Tobacco is the leading cause of preventable death nationwide. People who smoke are up to 6 times more likely than nonsmokers to have a heart attack. Tobacco also causes cancer. Up to 90% of lung cancer deaths are linked to smoking.

But the smoker isn’t the only one harmed by tobacco smoke. Secondhand smoke can make it more likely you’ll get heart disease, have a heart attack or die early. Smokers find it harder to quit if they’re around secondhand smoke. And kids exposed to secondhand smoke are more likely to become teenage smokers.

A team of NIH-funded scientists decided to take a closer look at how secondhand smoke affects the brains of young adults. About half of the study volunteers were nonsmokers. The rest were tobacco-dependent cigarette smokers.

Each volunteer sat in a car for 1 hour while a smoker puffed away on a cigarette to create secondhand smoke. On a different day, the volunteers had a 1-hour car session without being exposed to secondhand smoke. Their brains were scanned before and after each session.

The researchers discovered the addictive chemical nicotine—found in all tobacco products—both in the blood and attached to molecules in the brain after exposure to secondhand smoke. This nicotine binding was similar in smokers and nonsmokers. The smokers also had stronger cravings after being exposed to secondhand smoke.

“These results show that even limited secondhand smoke exposure delivers enough nicotine to the brain to alter its function,” says Dr. Nora D. Volkow, director of NIH’s National Institute on Drug Abuse.