Table 3. Predicting Wave 2 ever smoking from Wave 1 ever e-cigarette use – effects of confounder adjustment.

Table 3 first shows the unadjusted OR, and then the OR adjusted for the propensity score in two ways. Finally, it shows the results of a stepwise regression based on successively including the most significant adjustment variables.

Adjustment variables	OR (95% CI)
None	5.702 (4.334-7.502)
Propensity score as quintiles	2.476 (1.852-3.310)
Propensity score as continuous variable	2.474 (1.791-3.419)
Age range	4.806 (3.637-6.351)
+ Ever used alcohol at all	3.799 (2.855-5.055)
+ Ever been curious about smoking a cigarette	2.852 (2.123-3.831)
+ Think you will smoke a cigarette in the next year	2.185 (1.608-2.969)
+ Agree/disagree: Prefer friends who are exciting and unpredictable	2.111 (1.552-2.869)
+ Reaction if parent/guardian found you using tobacco	2.025 (1.489-2.756)
+ Gender	2.028 (1.489-2.761)
+ Agree/disagree; I think I would enjoy using tobacco	1.939 (1.420-2.648)
+ Agree/disagree: some products are safer than others	1.925 (1.406-2.635)
+ Ever used prescription drug not prescribed to you: Ritalin or Adderall	1.865 (1.360-2.557)
+ Has a Facebook, Google Plus, MySpace, Twitter or other social networking	1.852 (1.350-2.539)
+ Anyone who lives with you now use tobacco	1.847 (1.347-2.533)