Many behaviors, such as smoking, offer a variety of possible phenotypes that may have differing genetic components. Genomic scans for current smoking status [1,2], pack-years smoked [2], and nicotine dependence [3] and association studies for a variety of smoking-related behaviors have been conducted. Longitudinal data offer additional phenotypes, including the maximum number of cigarettes smoked per day over several years, a trait which may be more genetic than current smoking habits. We assessed evidence for the existence and localization of quantitative trait loci (QTLs) for "maximum number of cigarettes smoked per day" using data collected over 40 years in the Framingham Heart Study and the Framingham Offspring Study.
