Table 4.

Path estimates for residual genetic and environmental effects^a and total genetic and environmental influences on smoking, alcohol intoxication and illicit drug use^b

	Age (years)	Genetic factors						Shared environmental factors						Unique environmental factors
		A1	A2	A3	Ac	As	At	C1	C2	C3	Cc	Cs	Ct	E1	E2	E3	Ec	Es	Et
Smoking	13–14	0.31			46	10	56	0.13			31	2	33	−0.02			11	0	11
	16–17	−0.01	0.33		40	11	51	0.20	−0.01		26	4	30	0.28	0.12		9	9	18
	19–20	0.21	0.47	0.12	33	27	60	0.12	0.15	0.04	10	3	13	0.10	0.33	0.25	9	18	27
Alcohol intoxication	13–14	0.44			35	20	55	0.18			23	3	26	0.32			9	10	19
	16–17	−0.01	0.36		31	13	44	0.33	0.26		20	18	38	−0.05	0.32		7	10	17
	19–20	−0.10	0.22	0.58	18	40	58	0.06	0.16	−0.01	6	3	9	0.06	0.15	0.52	4	30	34
Illicit drug use	13–14	0.70			20	50	70	−0.04			13	0	13	0.68			5	13	18
	16–17	0	0.50		38	25	63	0.01	0.11		25	1	26	0.11	0.32		9	2	11
	19–20	0.02	0.37	0.41	43	31	74	−0.01	0.01	0.11	12	1	13	−0.05	0.03	0.05	12	1	13

A1, A2 and A3, additive genetic path estimates at ages 13–14, 16–17 and 19–20 respectively; A_c, percentage of genetic effects due to common factors; A_s, percentage of genetic effects due to specific factors; A_t, total genetic effects; C1, C2 and C3, shared environment path estimates at ages 13–14, 16–17 and 19–20 respectively; C_c, percentage of shared environmental effects due to common factors; C_s, percentage of shared environmental effects due to specific factors; C_t, total shared environmental effects; E1, E2 and E3, unique environment path estimates at ages 13–14, 16–17 and 19–20 respectively; E_c, percentage of unique environmental effects due to common factors; E_s, percentage of unique environmental effects due to specific factors; E_t, total unique environmental effects. Totals may not equal 100% due to rounding error.

^aResults for ‘ lower portion ’ of the model only (Fig. 1).

^bTotal genetic and environmental influences on smoking, alcohol intoxication, and illicit drug use at waves 2–4, including common and substance-specific/residual influences.