The number of peers who smoked was assessed by two questions of the form “How many of your four best _____ friends smoked cigarettes during high school?”: one for male and the other for female best friends. The response to both questions was summed providing a count variable of number of best friends who smoked from 0–8. These measures where adapted from the Teenage Attitudes and Practices Survey (TAPS) [26] to reflect the specific period of adolescence and are widely used to characterize level of peer smoking [27].
