Table 2.

Twin-pair and sibling-pair tetrachoric correlations for cigarette and cannabis use in African-Americans and European Americans.

	rMZ (MOAFTS)	rDZ (MOAFTS)	rFS (MOFAM)
African Americans	N=111 pairs	N=143 pairs	N=127 pairsa
Use of Cigarettes	0.59 (0.35 – 0.82)	0.28 (0.02 – 0.54)	0.33 (0.08 – 0.58)
Use of Cannabis	0.63 (0.42 – 0.84)	0.30 (0.06 – 0.54)	0.53 (0.28 – 0.77)
European Americans	N=853 pairs	N=663 pairs	N=126 pairsb
Use of Cigarettes	0.90 (0.86 – 0.93)	0.64 (0.54 – 0.73)	0.53 (0.31 – 0.75)
Use of Cannabis	0.80 (0.75 – 0.85)	0.57 (0.47 – 0.66)	0.61 (0.40 – 0.81)

NOTE: all correlations significant at p < 0.05

^aincludes 88 families with two siblings interviewed, and 13 families with three siblings interviewed (yielding three pairs of respondents each)

^bincludes 75 families with two siblings interviewed, and 17 families with three siblings interviewed (yielding three pairs of respondents each)