Table 3.

Linear regression of smoking heaviness at age 15 and educational attainment at age 16, before and after adjustment for potential confounders in ALSPAC (N = 2017)

Model	β coefficient	95% CI	p value
1	−2.517	−2.868 to −2.166	<0.001
2	−1.725	−1.969 to −1.482	<0.001
3	−1.749	−1.986 to −1.512	<0.001
4	−1.561	−1.800 to −1.321	<0.001
5a	−1.322	−1.645 to −0.999	<0.001
5b	−1.464	−1.751 to −1.176	<0.001
5c	−1.396	−1.664 to −1.129	<0.001
6	−1.254	−1.597 to −0.911	<0.001

Model 1 – Educational performance score (as % of total possible) at age 16 by a unit increase of 5-level smoking heaviness category at age 15; Model 2 – as model 1 with additional adjustment for educational attainment at age 11; Model 3 – as model 2 with additional adjustment for pre-birth confounders (gender, maternal education, maternal smoking, alcohol and cannabis use during pregnancy, maternal depression); Model 4 – as model 3 with additional adjustment for childhood confounders (truancy, hyperactivity, conduct problems, psychotic-like experiences, depression); Model 5a – as model 4 with additional adjustment for cannabis use at age 15; Model 5b – as model 4 with additional adjustment for alcohol use at age 15; Model 5c – as model 4 with additional adjustment for illicit drug use at age 15 Model 6 – as model 4 with additional adjustment for cannabis, alcohol and other illicit drug use at age 15.