Table 2

Unadjusted relative risk ratios for changes in susceptibility and smoking status in relation to explanatory variables 2011–2012

	Among non-susceptible never-smokers at baseline						Among susceptible never-smokers at baseline
	RRR of becoming susceptible			RRR of becoming an ever-smoker			RRR of becoming non-susceptible			RRR of becoming an ever-smoker
	Estimate	99% CI	p Value	Estimate	99% CI	p Value	Estimate	99% CI	p Value	Estimate	99% CI	p Value
Age
11	1.00			1.00			1.00			1.00
12	0.90	0.40 to 2.03	0.746	2.62	0.55 to 12.51	0.114	0.87	0.17 to 4.53	0.829	0.46	0.14 to 1.57	0.105
13	0.97	0.49 to 1.91	0.894	5.94	1.33 to 26.49	0.002	0.31	0.07 to 1.36	0.041	0.74	0.36 to 1.50	0.271
14	1.03	0.51 to 2.10	0.908	9.29	1.49 to 57.78	0.002	0.62	0.27 to 1.43	0.137	0.98	0.37 to 2.62	0.968
15
Parental smoking
Neither parent smokes	1.00			1.00			1.00			1.00
One parent smokes	1.73	0.99 to 3.04	0.011	2.94	0.83 to 10.43	0.028	1.84	0.61 to 5.59	0.158	2.68	1.27 to 5.64	0.001
Both parents smoke	1.37	0.48 to 3.96	0.441	3.29	1.06 to 10.24	0.007	1.17	0.22 to 6.27	0.814	2.61	1.78 to 5.77	0.002
Sibling smoking
None smokes	1.00			1.00			1.00			1.00
At least one smokes	1.57	0.51 to 4.86	0.303	2.42	0.62 to 9.53	0.096	1.38	0.33 to 5.80	0.568	3.77	1.10 to 12.84	0.005
Smoking in the main family home
Not allowed	1.00			1.00			1.00			1.00
Allowed	1.63	0.81 to 3.27	0.073	4.51	2.69 to 7.56	<0.001	1.23	0.33 to 4.56	0.683	1.20	0.31 to 4.72	0.727
Number of friends who smoke
None	1.00			1.00			1.00			1.00
One or two	1.97	0.80 to 4.87	0.055	2.85	0.58 to 14.07	0.090	0.58	0.10 to 3.44	0.415	1.03	0.24 to 4.39	0.961
Three or more	2.32	0.70 to 7.68	0.069	8.23	4.32 to 15.65	<0.001	0.41	0.05 to 3.36	0.276	2.67	1.06 to 6.73	0.006
Not sure	1.66	1.07 to 2.60	0.003	3.12	0.94 to 10.32	0.014	0.62	0.24 to 1.61	0.129	1.16	0.52 to 2.58	0.641
Self to perceived academic performance
Excellent or good	1.00			1.00			1.00			1.00
Average or below average	2.03	1.04 to 3.94	0.006	1.90	0.92 to 3.92	0.023	0.53	0.21 to 1.31	0.070	0.81	0.42 to 1.56	0.413
Rebelliousness
Low	1.00			1.00			1.00			1.00
High	1.73	1.27 to 2.35	<0.001	3.78	2.78 to 5.14	<0.001	0.87	0.55 to 1.39	0.452	2.17	0.63 to 7.51	0.107
Noticing point-of-sale displays in large shops
Sometimes or less	1.00			1.00			1.00			1.00
Most or every time	1.37	0.95 to 1.96	0.027	3.17	0.92 to 10.93	0.017	0.97	0.50 to 1.90	0.911	0.95	0.49 to 1.85	0.850
Frequency of visiting large shops
Less than 2 or 3 times a week	1.00			1.00			1.00			1.00
At least 2 or 3 times a week	0.58	0.43 to 0.78	<0.001	0.63	0.31 to 1.25	0.080	1.03	0.57 to 1.86	0.906	0.73	0.40 to 1.35	0.193
Noticing point-of-sale displays in small shops
Sometimes or less	1.00			1.00			1.00			1.00
Most or every time	1.23	0.93 to 1.63	0.062	2.42	1.17 to 5.00	0.002	0.66	0.20 to 2.22	0.377	1.39	0.63 to 3.08	0.279
Frequency of visiting small shops
Less than 2 or 3 times a week	1.00			1.00			1.00			1.00
At least 2 or 3 times a week	0.93	0.73 to 1.18	0.433	0.36	0.29 to 0.46	<0.001	1.01	0.56 to 1.84	0.950	0.37	0.12 to 1.11	0.020
Number of brands recognised
None	1.00			1.00			1.00			1.00
1–5	1.64	0.87 to 3.08	0.044	2.24	0.91 to 5.53	0.021	0.98	0.25 to 3.82	0.976	2.05	0.71 to 5.94	0.081
More than 5	2.67	1.65 to 4.33	<0.001	6.07	2.38 to 15.46	<0.001	0.60	0.20 to 1.78	0.227	2.78	0.75 to 10.32	0.044

Sex and quintiles of Index of Multiple Deprivation not presented as these were not significant predictors for any of the outcome variables.
RRR, relative risk ratios.