Variables entered in the regression model
| 1 Smoking behaviour of best friend: 0 = non-smoker; 1 = smoker. |
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| 2 Smoking behaviour of elder brother: 0 = non-smoker; 1 = smoker. |
| 3 Attitude of family towards pupil’s smoking behaviour: summed score of attitudes of father, mother, elder brother, elder sister, recoded as dummy variable. |
| 4 Attitude of best friend towards pupil’s smoking behaviour: 0 = positive; 1 = don’t care; 2 = negative. |
| 5 Alcohol use: 0 = never; 1 = at least once a month. |
| 6 Feeling about school: 0 = like it a lot; 1 = like it a bit; 2 = don’t like it very much; 3 = don’t like it at all. |
| 7 Being truant: 0 = never; 1 = seldom; 2 = more than once a month. |
| 8 Usually arriving late in class: 0 = strongly disagree; 1 = disagree; 2 = depends-agree. |
| 9 Taking part in bullying other students in school: 0 = never; 1 = once or twice; 2 = sometimes; 3 = more than once a week. |
| 10 Feeling pressured by school work: 0 = not at all; 1 = a little; 2 = some/a lot. |
| 11 Coffee consumption: 0 = rarely/never; 1 = more than once a week; 2 = more than once a day. |
| 12 Wearing helmet on motorbike: 0 = always; 1 = often; 2 = sometimes; 3 = never. |
| 13 Watching videotapes: 0 = never; 1 = more than 1 hour/week; 2 = 1–3 hours/week; 3 = 4 or more hours/week. |
| 14 Psychosomatic symptoms: sum score of six items, recoded as dummy, split percentile 50. |
| 15 Using medication: sum score of six items, recoded as dummy variable, split percentile 50. |