Table 2.

Polychoric twin pair correlations (and 95% confidence intervals) for conduct symptoms, and alcohol, cannabis, and tobacco use, estimated in Mx (corrected for age and sex effects).

Zygosity	N pairs	Conduct symptoms	Tobacco use	Alcohol use	Cannabis use
MZ M	113–178	0.60 (0.46; 0.71)	0.81 (0.71; 0.88)	0.53 (0.36; 0.66)	0.79 (0.63; 0.89)
DZ M	85–151	0.39 (0.21; 0.55)	0.45 (0.21; 0.64)	0.26 (0.02; 0.46)	0.63 (0.36; 0.80)
MZ F	145–183	0.83 (0.73; 0.89)	0.77 (0.66; 0.84)	0.48 (0.32;0.60)	0.73 (0.52; 0.86)
DZ F	98–128	0.51 (0.30; 0.68)	0.55 (0.33; 0.70)	0.21 (−0.01; 0.41)	0.52 (0.23; 0.73)
DZ OS	168–262	0.33 (0.16; 0.48)	0.55 (0.39; 0.68)	0.29 (0.12; 0.43)	0.47 (0.27; 0.63)

F=female, M=male, MZ =monozygotic, DZ=dizygotic, OS=opposite-sex