Table 4.

Genetic (r_A), family environmental (broad; r_C), and non-shared environmental (r_E) correlations between cigarette use and cannabis use in African-American and European American twins and sibling pairs.

	Cross-substance rA	Cross-substance rC	Cross-substance rE
African-Americans	0.82 (−1.00 – 0.91)	0.75 (−1.00 – 1.00)	0.48* (0.20 – 0.79)
European Americans	0.89* (0.71 – 1.00)	0.70* (0.26 – 1.00)	0.66* (0.41 – 0.83)

Note: r_A=additive genetic correlation, r_C=family and twin-specific environmental correlation, r_E=non-shared environmental correlation.

^*indicates p < 0.05