and 57.7% were female. When asked how they would describe their racial backgrounds, 82.5% endorsed Black/African American, with the remainder of the sample endorsing Asian, American Indian or Alaska Native. To reduce stratification, only those who described their backgrounds as African American were included in the present analyses. In addition, only individuals who had smoked cigarettes during their lifetime were included in analyses so that genetic and environmental influences on the decision to initiate cigarette smoking are not confounded with genetic and environmental influences on current frequency of cigarette use.
