Phenotypic and genetic factors in motives for smoking

Underlying phenotypic and genetic factors involving motives for smoking wer e assessed using data from 1756 twins, including 390 complete pairs. Respon dents were aged 50 or older and included both current and former smokers. T he Motives for Smoking Questionnaire (MSQ) hypothesizes eight correlated bu t distinct motives for smoking, which correspond to pharmacological and non pharmacological second-order factors. This paper concentrates on the pharma cological motives. Principal-factor analysis recovered five categories. Ite ms constituting Sedative, Stimulative, and Addictive reasons for smoking me rged into one factor, whereas Automatic smoking, also considered to have ph armacological origins, formed a separate factor. Twin analysis was used to test for genetic effects and to determine whether these factors, although c ombined phenotypically, were affected by distinct genetic or environmental influences. Genetic effects accounted for a significant amount of the varia nce in the four hypothesized pharmacological motives for smoking, as did sh ared environment. The separate factor for Automatic smoking in the phenotyp ic analysis was due to environmental effects, and shared environment was a greater influence on Automatic smoking for women than men, One common effec t explained the genetic variance; no genetic influence uniquely affected an y specific motive. Therefore, individual differences in the hypothesized ph armacological motives for smoking appear to originate from a common genetic pathway.