All outcome variables related to cigarette use are lifetime measures constructed from each individual's sequential set of direct interviews. The criteria for each of the ever/never measures were examined on each of the interviews in turn and were assessed independently of any other interview(s). Once the criteria for a given measure were met, the variable was coded as present (even if the criteria were not met on a subsequent assessment). The corresponding AAO variable was set to the age reported on and/or computed from the interview on which the subject first met criteria for the lifetime measure.
