A study of smokers who suffered strokes has shown that part of the brain, the insula, appears to be intimately involved in their addiction, indicating that it could be targeted to help people to give up the habit.

Patients who had strokes that damaged the insula, which is thought to be involved in emotions and cravings, lost the urge to smoke immediately, and many have not touched a cigarette since.

The findings suggest the possibility of helping smokers to give up by manipulating the insula to kill their addiction, without causing the extensive brain damage of a stroke.

Drugs could be developed to alter its activity, or it could be disrupted using magnetic fields. Another technique called deep brain stimulation, in which electrodes are implanted in the brain to switch off particular areas, has already been used successfully to treat Parkinson’s disease and depression.

Such treatments, however, will require much more research into exactly how the insula affects smoking and other addictions before patient trials could begin; it will be important not to disrupt other activities in which the region plays a critical role.

The insula lies in the centre of the brain and is thought to translate information from other parts of the body into feelings such as hunger, pain or cravings for a drug.

“The insula also carries out lots of normal everyday functions, so we would want to make sure we only interfere with functions that disrupt bad habits like smoking but not something vital like eating,” said Antoine Bechara, of the University of Southern California (USC) and the University of Iowa, who led the research.

Nevertheless, the work is exciting because damage to the insula appears to break many smokers’ habits instantly; their brains seem to forget that they are supposed to crave cigarettes.

“There is a lot of potential for pharmacological developments,” Dr Bechara said. “One of the most difficult problems in any form of addiction is the difficulty in stopping the urge to smoke, to take a drug, or to eat for that matter. Now we have identified a brain target for further research into dealing with that urge.”

Antonio Damasio, Professor of Neuroscience at USC, who first suggested the insula’s role in feelings, said: “It’s really intriguing to think that disrupting this region breaks the pleasure feelings associated with smoking. It is immediate. It’s not that they smoke less. They don’t smoke, period.”

The study, pubished today in the journal Science, was inspired by a patient who smoked 40 cigarettes a day before having a stroke that damaged his insula. He quit immediately, telling doctors that he “forgot the urge to smoke”.

The scientists then turned to a database of stroke patients held by the University of Iowa and identified 69 who had smoked at least five cigarettes a day for at least two years before they suffered brain damage. They found that 19 of these patients had damage to the insula and 13 of them had given up smoking, 12 of them quickly and easily. The other six continued to smoke — possibly reflecting damage to different parts of the insula.

Of the 50 patients who had strokes that did not disrupt the insula, 19 also gave up smoking, but only four did so instantly and without any cravings.

The difference in the two groups’ experience of quitting suggests that the general stroke patients gave up in standard fashion because of the health risks. The insula-damaged patients, however, gave up because it no longer occurred to them to smoke.

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