Table 3.

Hazard Ratios (and 95% Confidence Intervals) from Cox Regression models predicting timing of substance involvement from parental alcoholism and parental separation in African ancestry twins, unadjusted and adjusted for family background, offspring psychopathology, and childhood risk-factors.

	Alcoholic/Separated		Alcoholic/Intact		Nonalcoholic/Separated
	Unadjusted (n = 208)	Adjusted (n = 174)	Unadjusted (n = 47)	Adjusted (n = 42)	Unadjusted (n = 269)	Adjusted (n = 210)
Alcohol use	1.03 (0.73 – 1.46)	0.78 (0.52 – 1.17)	1.06 (0.68 – 1.65)	1.04 (0.61 – 1.77)	0.94 (0.67 – 1.31)	0.94 (0.64 – 1.36)
Alcohol intoxication
< 15	1.48 (0.88 – 2.50)	4.54 (0.37 – 54.93)a	0.99 (0.43 – 2.67)	8.13 (0.66 – 100.07)	0.93 (0.55 – 1.59)	7.90 (0.69 – 91.06)
≥ 15	⊥	0.76 (0.39 – 1.47)a	⊥	0.64 (0.23 – 1.80)a	⊥	0.62 (0.33 – 1.18)
Cigarettes use
< 15	1.88 (1.26 – 2.81)	1.66 (0.89 – 3.09)	1.30 (0.80 – 2.12)	0.79 (0.44 – 1.42)	1.09 (0.76 – 1.55)	0.93 (0.61 – 1.41)
≥ 15	1.07 (0.66 – 1.75)	0.88 (0.52 – 1.47)	⊥	⊥	⊥	⊥
Regular smoking
< 15	2.84 (0.87 – 9.26)	3.22 (0.30 – 34.34)	⊤	⊤	⊤	1.95 (0.18 – 21.42)a
15-17	1.01 (0.40 – 2.52)	0.25 (0.08 – 0.74)	0.52 (0.14 – 1.88)	0.25 (0.06 – 0.96)	1.09 (0.50 – 2.38)	0.40 (0.14 – 1.19)a
≥ 18	⊥	⊥	⊥	⊥	⊥	0.08 (0.02 – 0.37)
Cannabis use	1.36 (0.85 – 2.20)	0.91 (0.50 – 1.69)	1.32 (0.71 – 2.45)	1.07 (0.52 – 2.21)	1.50 (0.95 – 2.35)	1.24 (0.68 – 2.23)
Other illicit drug use
< 15	0.69 (0.22 – 2.23)	0.48 (0.03 – 8.85)	0.71 (0.14 – 3.69)	0.03 (0.01 – 0.18)	0.73 (0.23 – 2.23)	0.07 (0.01 – 0.63)
≥ 15	⊥	0.04 (0.01 – 0.21)	⊥	⊥	⊥	1.07 (0.24 – 4.77)

Note. Reference group = nonalcoholic, intact families. Where brackets are shown, reported risk is equivalent across risk periods (age in years).

^aPost-hoc test equating hazard ratios across risk periods did not show significant heterogeneity (p > 0.05), but the proportional hazards assumption was violated and thus an age interaction was modeled with separate hazard ratios reported.