If numerous cold turkey, nicotine patch, and vaping attempts to give up smoking haven’t worked, then you might be able to blame your brain, says a new study out of the Medical University of South Carolina.

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Researchers found a brain circuit associated with automatic, or habitual, behavior — like driving or smoking. “A pack-a-day smoker places a cigarette in their mouth a few hundred times a day over years, so they have many trials of experience,” says lead study author Brett Froeliger in a statement. “It becomes automated.”

A section of the brain known as the inhibitory control network helps you stop these habits. To test whether this pathway affected smoking cessation, researchers used functional MRI to study the brains of 81 adults who played a game that trained them to respond automatically before inhibiting the response. Participants had to strike a computer key every time a colored circle appeared with the exception of a particular color. All subjects were committed to give up smoking and on a 10-week program aimed to help.

About half were able to quit smoking. These people had to use fewer resources in their brains to stop their automatic reactions, seemingly making it easier. Patients who relapsed scored as well as those who quit successfully, but it was much harder for them to do so.

In a second study, 26 smokers were given their favorite brand of cigarettes, lighter and ashtray with the instructions that they’d receive $1 for every six minutes they went without lighting up. Similarly, those who resisted temptation longer had lower responses across the network as well as stronger functional connectivity.

“This work helps scientists understand why some smokers have a harder time quitting,” says Froeliger in a release. “Individual differences in brain biology are important.”

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In the United States, about 36.5 million adults smoke, however the numbers are declining. In 2015, about 15 out of 100 adults smoked compared to nearly 21 out of 100 people in 2005, estimates the Centers for Disease Control and Prevention. According to WebMD, about 90 percent of smokers try to quit without the use of aids like patches. Only four to seven percent are successful.

This is the first study to link smoking with the strength of a brain circuit to inhibit automated behavior. Researchers believe this can help with developments to help smokers finally give up the habit and help explain why some people have more success quitting than others.

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