Impact of the age restriction law on regular smoking*
| Adjusted OR (95% CI) | VIF | p Value | |
| FSM | 1.87 (1.66 to 2.11) | 1.23 | 0.0005 |
| Law | 0.67 (0.55 to 0.81) | 3.00 | 0.0005 |
| Law*FSM | 1.29 (0.95 to 1.76) | 1.38 | 0.102 |
| Age | 1.74 (1.67 to 1.81) | 1.32 | 0.0005 |
| Year | 1.02 (0.98 to 1.06) | 2.83 | 0.325 |
| Male | 0.54 (0.50 to 0.58) | 1.00 | 0.0005 |
| White ethnicity | 1.53 (1.31 to 1.78) | 1.08 | 0.0005 |
| Ever alcohol use | 5.81 (4.75 to 7.12) | 1.45 | 0.0005 |
| Ever drug use | 10.99 (9.98 to 12.10) | 1.15 | 0.0005 |
| Constant | −12.94 | 0.0005 |
* Smoking at least one cigarette per week.
FSM, pupils eligible for free school meals; VIF, variance inflation factor.