Brain structure key to smoking addiction 

Scientists who noticed that one heavy smoker suddenly lost all desire for cigarettes after suffering brain damage in a stroke have identified a structure deep in the brain as a key player in smoking addiction.

Writing in the journal Science on Friday, they said the findings about the brain structure called the insula could lead to therapies targeting it to help people kick the habit.

Smoking is the most common preventable cause of death and disease in the developed world, with people hooked by highly addictive nicotine that makes it very hard for many to quit.

"It's a very significant finding because it kind of shifts attention to an area that we were not looking at seriously before," one of the researchers, Antoine Bechara of the University of Southern California and the University of Iowa, said in an interview.

The insula, roughly the size of a large coin, gets signals from elsewhere in the body and is believed to help convert this information into feelings such as hunger, pain or craving.

Bechara, who long has studied the complex phenomenon of addiction, speculated the insula may be involved in addictions to alcohol and drugs, and maybe even obesity.

He said one patient drove the researchers' interest in the insula -- a man who started smoking at age 14 and eventually puffed 40 cigarettes a day.

"Even when he was hospitalized on occasion for other medical reasons, he used to go outside to smoke," Bechara said.

Switch went off

But after a stroke left the man's insula damaged, "it was like a switch went off" and he never wanted a cigarette again, Bechara said.

The researchers said the man told them his "body forgot the urge to smoke" and that he even found the smell of cigarette smoke disgusting.

The researchers used a University of Iowa registry of patients to see if other smokers with insula damage experienced the same thing. They focused on 69 people who had smoked more than five cigarettes per day for more than two years before suffering brain damage.

Of these, 19 had insula damage. After suffering the insula damage, 13 of the 19 quit, with all but one doing it instantly and effortlessly.

The researchers do not know why the six others continued smoking. Some smokers in the registry with other types of brain damage also quit, but those with insula damage were the most likely to give up the habit.

The researchers think damage to the insula cut the urge to smoke rather than decreasing the pleasure smokers get. The researchers were unable to study whether insula damage affected other types of drug addiction but noted it had no apparent impact on the desire to eat.

The US National Institutes of Health funded the study. Dr Nora Volkow, director of the NIH's National Institute on Drug Abuse, called the finding "absolutely fascinating."

"It does provide the question: Are there targets that we could identify that are uniquely expressed in this area of the brain such that we could tailor treatments?" Volkow said in an interview.

Because the insula is involved in many normal functions, Bechara said, scientists who try to find a way to target it to help people quit smoking must be careful to disrupt only bad habits and not critical activities like eating.