London Free Press

You don't have to smoke cigarettes to crave them, a U.S. study says.

According to the National Institute on Drug Abuse (NIDA), exposure to second-hand smoke produces the same effects on the brain as actually smoking -- and that includes nicotine cravings.

The study looked at the effects of second-hand smoke on 24 young adults, some smokers and some non-smokers.

The researchers used positron emission tomography scanning -- an imaging technique that generates a three-dimensional image of functional processes in the body -- to examine the smoke's effect on the subjects' brains.

They found second-hand smoke in an enclosed space is enough to bind to receptors that are normally targeted by direct exposure to tobacco smoke.

"These results show that even limited second-hand smoke exposure delivers enough nicotine to the brain to alter its function," NIDA director Nora D. Volkow said in a statement released by the National Institutes of Health, which funded the research.

The study points to earlier research that shows teenagers are more likely to take up smoking if they were exposed to second-hand smoke as children.

What's more, smokers who were around smoke as kids have a harder time kicking the habit as adults.

"Chronic or severe exposure could result in even higher brain nicotine levels, which may explain why second-hand smoke exposure increases vulnerability to nicotine addiction," said Volkow.

"This study gives concrete evidence to support policies that ban smoking in public places, particularly enclosed spaces and around children," said Arthur Brody, one of the study's authors.

The study was published in the Archives of General Psychiatry.