When it comes to quitting smoking, some people find it easier than others. Now, new research from Pennsylvania State University, recently published in the journal Cognitive, Affective and Behavioral Neuroscience may explain why.

The research team, including Stephen J. Wilson, assistant professor of psychology at Penn State, found that activity in the reward system of the brain - known as the striatum - could be a predictor of how likely a smoker is to quit the habit.

As of 2012, approximately 18.1% of Americans aged 18 or over smoked cigarettes - a reduction from the 20.9% of American adults who smoked in 2005.

Such a reduction has been partly attributed to smoking cessation aids, such as nicotine replacement therapy - the administration of nicotine to the body using means other than tobacco. This can include nicotine patches, gum, nasal spray and lozenges.

However, it is easier for some people to quit smoking than others. A 2011 report from the US Centers for Disease Control and Prevention (CDC) revealed that of 52.4% adult smokers who said they attempted to quit in the past year, only 6.2% were successful.

fMRI imaging measured smokers' response to monetary rewards

In an attempt to determine why some smokers find it so hard to quit, the researchers decided to conduct an experiment on 44 smokers.

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Researchers say that activity in the reward system of the brain - known as the striatum - could be a predictor of how likely a smoker is to quit the habit.

All participants were between the ages of 18 and 45 and reported smoking a minimum of 10 cigarettes a day for the past year. Subjects were asked to refrain from smoking and using any other nicotine-containing products 12 hours prior to the start of the experiment.

For the test, the researchers used functional magnetic resonance imaging (fMRI) to observe activity in the striatum of the brain as participants played a card-guessing game that offered them the chance to win money. According to Wilson, the striatum is the "area of the brain that is important for motivation and goal-directed behavior - functions highly relevant to addiction."

All participants were told they would have to wait around 2 hours - until the experiment had finished - to have a cigarette. But during the experiment, half of the subjects were informed a mistake had been made and they could now have a cigarette during a 50-minute break that would take place in the next 16 minutes.

When it was time for the cigarette break, these participants were then told that for every 5 minutes they refrained from smoking, they would receive $1. Overall, they had the potential to earn up to $10.

Weaker activity in striatum may explain smokers' difficulty in quitting

The researchers report that smokers who were unable to refrain from smoking in response to monetary rewards during the break showed weaker activity in the striatum in response to monetary rewards during the card-guessing game.

"We believe that our findings may help to explain why some smokers find it so difficult to quit smoking," says Wilson. "Namely, potential sources of reinforcement for giving up smoking - for example, the prospect of saving money or improving health - may hold less value for some individuals and, accordingly, have less impact on their behavior."

He adds that the findings could lead to the development of new strategies to help smokers give up the habit:

"Our results suggest that it may be possible to identify individuals prospectively by measuring how their brains respond to rewards, an observation that has significant conceptual and clinical implications.

For example, particularly 'at-risk' smokers could potentially be identified prior to a quit attempt and be provided with special interventions designed to increase their chances for success."

Medical News Today recently reported on a study published in the journal Cancer Epidemiology, Biomarkers & Prevention, which claims to identify factors that could predict how likely teenage smokers are to quit the habit.