Even with the help of nicotine replacement therapy and other smoking cessation aids, some smokers are just unable to quit the habit. According to a new study by researchers from Duke Medicine in Durham, NC, it may be because their brains are not hard-wired to.

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Smokers who successfully quit the habit were found to have greater connectivity between brain regions linked to cravings and motor control than those who failed to quit.

Published in the journal Neuropsychopharmacology, the study reveals that smokers who successfully quit showed greater connectivity between brain regions associated with cravings and motor control, compared with smokers who tried to quit but failed.

The research team, led by Meredith Addicott, PhD, an assistant professor at Duke, says the findings suggest that increasing connectivity between these brain regions may boost a smoker's quitting success.

While smoking rates in the US have fallen in recent years, 17.8% of adults and almost 10% of youths still smoke.

Smoking remains a major public health concern, raising the risk of a number of health conditions, including lung cancer, heart disease and stroke. It is the leading cause of preventable death in the US, accounting for more than 480,000 deaths in the country every year.

According to the American Cancer Society, only around 4-7% of smokers who try to quit the habit without help are successful. Among those who use smoking cessation aids - such as nicotine replacement therapy, behavioral therapy or medication - around 25% are smoke-free for at least 6 months.

For their study, Prof. Addicott and colleagues set out to see whether there may be a neurological explanation as to why some smokers are successful in quitting while others are not.

Greater connectivity between the insula, somatosensory cortex among successful quitters

To reach their findings, the team used magnetic resonance imaging (MRI) to analyze the brain activity of 85 smokers 1 month before they attempted to quit.

From monitoring the smokers' progress during the 10 weeks after their quit date, the team found that 44 smokers quit the habit successfully and 41 relapsed.

On looking at the brain scans taken prior to the smokers' quit attempt, the researchers found that the participants who successfully quit smoking showed greater coordinated activity, or synchrony, between the insula (responsible for processing urges and cravings) and the somatosensory cortex (important for motor control and sense of touch) than smokers who failed to quit.

"Simply put, the insula is sending messages to other parts of the brain that then make the decision to pick up a cigarette or not," explains Prof. Addicott.

The researchers note that numerous smoking cessation studies have investigated the role of the insula - a part of the cerebral cortex - and have revealed that this brain region is active when smokers have the urge to smoke. Research has also revealed that damage to the insula results in reduced smoking cravings.

Senior study author Joseph McClernon, an associate professor at Duke, says their findings provide a "blueprint" for a potential smoking cessation strategy. He adds:

"There's a general agreement in the field that the insula is a key structure with respect to smoking and that we need to develop cessation interventions that specifically modulate insula function. But in what ways do we modulate it, and in whom?

Our data provides some evidence on both of those fronts, and suggests that targeting connectivity between insula and somatosensory cortex could be a good strategy."

The team notes, however, that further research is required to determine exactly how greater connectivity between the insula and somatosensory cortex increases a smoker's likelihood of quitting.

Last month, Medical News Today reported on a study published in Nature Communications that detailed the discovery of a brain circuit that increases anxiety during nicotine withdrawal.