Table 3.

Standardized proportions of variance [95% Confidence Intervals] attributable to additive genetic, shared environmental, and non-shared environmental influences for the final model examining the genetic and environmental contributions to the comorbidity between cigarette and cannabis use in African-American and European-American twin and sibling pairs.

	Additive Genetic	Broad Family Environment (C+T)	Non-shared Environment
African-Americans
Use of Cigarettes	0.52 (0.00 – 0.73)	0.02 (0.00 – 0.47)	0.45* (0.27 – 0.76)
Use of Cannabis	0.43 (0.00 – 0.78)	0.15 (0.00 – 0.55)	0.42* (0.22 – 0.67)
European Americans
Use of Cigarettes	0.66* (0.46 – 0.88)	0.23* (0.03 – 0.43)	0.11* (0.07 – 0.15)
Use of Cannabis	0.52* (0.32 – 0.72)	0.29* (0.09 – 0.45)	0.19* (0.15 – 0.25)

^*Indicates variance component significant at p < 0.05