The long-term brain changes observed among cocaine and heroin users can also be found in the brains of smokers, researchers from the National Institute on Drug Abuse (NIDA) say.

The Sydney Morning Herald reported Feb. 21 that the changes to smokers' brains could be observed even years after they quit. Researchers led by NIDA's Bruce Hope found abnormally high levels of a pair of enzymes involved in the dopamine system.

The fact that the changes were the same among smokers as among other drug users "strongly suggests" that they contribute to addiction, said Hope.

The study was slated to be published in the Journal of Neuroscience.