However, according to the epidemiological approach, the aim of primary prevention, regarding the use of illicit substances, is to ensure that a process (such as smoking) does not develop to a point of risk or severity. Flay, Hu and Richardson suggest primary prevention of smoking should involve prevention of experimental use, such as the experimentation/addiction stage proposed by Mayhew, Flay and Mott.9 Therefore, the investigators in this study chose to examine, as early stages of smoking, the pre-contemplation stage through the experimentation/addiction stage, as described above