. Author manuscript; available in PMC: 2016 Sep 1.

Published in final edited form as: Alcohol Clin Exp Res. 2015 Aug 6;39(9):1740–1748. doi: 10.1111/acer.12829

Table 4.

Within-pair contrasts for monozygotic and dizygotic twin pairs discordant for early risky behaviors.

	N (in pairs)	Model 1¹	Model 2²	Model 3³
Early Alcohol Experimentation	288	1.89 (1.26– 2.83)^*	2.08 (1.36– 3.17)^*	1.93 (1.22– 3.05)^*
Early Regular Alcohol Use	116	2.64 (1.32– 5.28)^*	2.85 (1.39– 5.83)^*	2.54 (1.22– 5.29)^*
Early Nicotine Experimentation	439	1.51 (1.09– 2.10)^*	1.53 (1.10– 2.15)^*	1.38 (0.97– 1.95)
Early Regular Nicotine Use	202	1.31 (0.78– 2.18)	1.32 (0.77– 2.25)	1.16 (0.67– 2.02)
Early Daily Nicotine Use	181	1.00 (0.59– 1.68)	0.99 (0.58– 1.71)	0.86 (0.49– 1.52)
Early Cannabis Experimentation	142	1.55 (0.88– 2.72)	1.49 (0.84– 2.64)	1.00 (0.53– 1.89)
Any Early Nicotine/Cannabis Experimentation	440	1.48 (1.07– 2.04)^*	1.49 (1.07– 2.08)^*	1.34 (0.95– 1.89)
Any Early Substance Experimentation	454	1.59 (1.14– 2.22)^*	1.62 (1.15– 2.28)^*	1.62 (1.15– 2.28)^*
Early Sex	193	1.17 (0.71– 1.92)	1.16 (0.70– 1.91)	0.94 (0.55– 1.61)

Note. In all comparisons, the non-early using cotwin is the referent group. 95% confidence intervals are presented in parentheses. Statistically significant effects that survive Bonferroni correction (p<.013) are bolded.

Significant before Bonferroni correction (p<.05).

Unadjusted model.

Adjusted for age, BMI, and early menarche.

Adjusted for age, BMI, early menarche, and other early risky behaviors (three out of four early alcohol experimentation, early nicotine experimentation, early cannabis experimentation, early sex- excluding the early risky behavior that was used as the exposure variable).