At this time of year many smokers will be trying to quit, and a recent study suggests that some will find it harder than others. Most smokers believe that smoking improves concentration and, undoubtedly, withdrawal symptoms cause feelings of irritability and agitation that make concentration difficult. When nicotine levels fall, smokers experience withdrawal symptoms which can only be alleviated by another cigarette. Scientists at the Abramson Cancer Center and Department of Psychiatry in the University of Pennsylvania School of Medicine had previously shown that smokers with a polymorphism in the catechol-O-methyltransferase (COMT) gene that results in a methionine to valine substitution suffer more from concentration problems associated with nicotine withdrawal. COMT is one of a number of enzymes that degrade catecholamines such as dopamine, and individuals with the valine COMT variant degrade dopamine at a faster rate than those with the methionine variant. The group has now used functional magnetic resonance imaging to examine brain function in smokers both during periods of abstinence and normal smoking. During the brain scans, the subjects were asked to hold in their minds a series of complex geometrical figures. The results showed that smokers with the valine variant suffered greater deficits in working memory and brain function when they had refrained from smoking for 14 or more hours, and this group also reported more severe withdrawal symptoms. The findings are published in the journal Molecular Psychiatry.
Smokers with the valine COMT variant are less responsive to existing therapies for smoking cessation and the study suggests that this group could be helped to quit by COMT inhibitors.