DNA methylation patterns in alcoholics and family controls

Table 4 Global methylation score sib-pair differences for non-smokers vs sibship with alcoholic tobacco user (7 sib pairs)

	Sib pair concordance for smoking status
	Concordant		Discordant
	Both non-smokers	Both smokers	Proband smokes
Mean (SD) sib pair difference in methylation at each site (alcoholic minus non-alcoholic sibling methylation level)	+0.006 (0.018)	+0.010 (0.020)	-0.009 (0.025)

Mean sib pair difference for 1287 markers, ANOVA: F = 284 (df = 2), P < 0.0001. Among concordant non-smoking sib pairs, for 6 of 7 pairs alcoholic subject had higher methylation index among concordant. Five of 7 smoking sib pairs alcoholic subjects had higher methylation index. Among discordant pairs with an alcoholic smoker, 6 of 7 alcoholic subjects had a lower methylation index than non-alcoholic siblings.