Scientists have identified a region of the brain that may hold the key to helping people quit smoking and to treating other forms of addiction.
Researchers in two studies have found that smokers who suffered a stroke in the insular cortex were far more likely to quit smoking and experience fewer and less severe withdrawal symptoms than those with strokes in other parts of the brain.
"These findings indicate that the insular cortex may play a central role in addiction," said lead author Amir Abdolahi, who conducted the research while he was a doctoral student at the University of Rochester School of Medicine and Dentistry.
"When this part of the brain is damaged during stroke, smokers are about twice as likely to stop smoking and their craving and withdrawal symptoms are far less severe," said Abdolahi, who is now at Philips Research North America.
The frontline prescription drugs currently used to treat tobacco dependence - which include bupropion and varenicline - primarily target the brain's "reward" pathways by interfering with the release and binding of dopamine in the brain in response to nicotine.
While these drugs are generally well-tolerated, they have relatively high rates of relapse.
Recent studies have hinted that a specific part of the brain - a central region called the insular cortex - may also play an important role in the cognitive and emotional processes that facilitate drug and tobacco use.
Researchers in the current set of studies tested this theory by determining whether smokers whose insular cortex had been damaged during a stroke are more likely to quit smoking.
They examined two different sets of indicators - whether patients have resumed smoking after a stroke and the severity of their craving for a cigarette during their hospitalisation.
The studies involved 156 stroke patients who were admitted to three hospitals and were identified as active smokers. The location of the stroke for each patient was determined by MRI and CT scans.
The study participants were divided into two groups - those with a stroke occurring in the insular cortex and those with a stroke in another part of the brain.
While recovering in the hospital the researchers measured the participant's level of smoking withdrawal. Because hospitalisation essentially constitutes a period of forced abstinence from smoking, this was an ideal environment to measure the severity of withdrawal symptoms.
The researchers found that patients with strokes occurring in the insular cortex had fewer and far less severe withdrawal symptoms than those with strokes in other parts of the brain.
The researchers followed the study participants for three months to determine whether or not they had resumed smoking.
Almost twice as many patients with strokes in the insular cortex quit smoking compared to those with strokes in other parts of the brain - 70 per cent vs 37 per cent.
The studies were published in the journals Addiction and Addictive Behaviours.
