Injury to a specific part of the brain called the insula can cause some people to simply 'forget' the urge to smoke, U.S. researchers say.

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SYDNEY: Injury to a specific part of the brain causes some people to 'forget' the urge to smoke, according to U.S. researchers.

Published in the current issue of the U.S. journal Science, a study led by Antoine Bechara of the University of Southern California in Los Angeles found that smokers with damage to a part of the brain called the insula may have their addiction to nicotine practically eliminated without the struggles reported by most who quit smoking.

"The researchers found that smokers with insula lesions were 136 times times more likely to have their addiction to nicotine erased than smokers with other brain injuries," said Nora Volkow, director of the U.S. National Institute on Drug Abuse, which funded the study. "Research that identifies a way to alter the function of this area could have major implications for smokers and addiction treatment in general."

Bechara and his colleagues identified 19 smokers who had experienced some degree of brain damage resulting in lesions on the insula, or insular cortex, which is located centrally in each hemisphere. Of these, 13 had quit smoking after the injury. The scientists also identified 50 smokers whose brain injuries did not include damage to the insula. Of these, 19 had stopped smoking.

While individuals from both groups were able to quit smoking, some smokers experienced a greater ease in quitting. The scientists developed four behavioural criteria for determining which smokers quit most easily; those who reported (1) quitting smoking less than one day after the brain injury; (2) their difficulty of quitting was less than three on a scale of one (easiest) to seven (most difficult); (3) that they did not smoke again after quitting; and (4) no urge to smoke since quitting.

The researchers found that 12 of the 13 participants who quit smoking following damage to their insula met these criteria as compared to only four of 19 participants who quit smoking after sustaining damage to other brain areas.

"Participants with damage to the insula were overwhelmingly more likely to experience a true disruption of the urge to smoke, characterised by an almost immediate cessation of smoking with no reported struggles to maintain their abstinence," said Bechara.

"We know that the insula plays a role in the desire to smoke by anticipating physical effects brought on by emotions such as those induced by environmental cues. Thus, damage to the insula could lead smokers to feel that their bodies have 'forgotten' the urge to smoke," he said.

According to Volkow, "Cigarette smoking is the most common preventable cause of illness and death in the modern world, and it is an addictive behaviour. While additional research is needed to replicate these findings, the current study suggests that damage to the insula can impact the conscious 'urge' to smoke, making it easier for smokers to quit and remain abstinent. Medications that target receptors within the insula may offer promise in developing more effective smoking cessation therapies in the future."