. Author manuscript; available in PMC: 2019 Jun 17.

Published in final edited form as: Drug Alcohol Rev. 2018 Mar 5;37(4):546–556. doi: 10.1111/dar.12679

Table 2:

Multivariate predictors of transitions to alcohol and cannabis use and use disorder, Australia

	Commencing use		Use to abuse (w/o prior dependence)		Use to dependence

	OR	(95% CI)	OR	(95% CI)	OR	(95% CI)
Alcohol	*N=8,463*		*N=7,945*		*N=7,945*

Individual’s age of commencing alcohol use³
Early youth	-	-	2.63^*	(2.09–3.31)	3.21^*	(2.10–4.91)
Mid-teens	-	-	1.37^*	(1.07–1.76)	1.71^*	(1.06–2.75)
Adulthood	-	-	1.00	-	1.00	-
χ²₂ [p]	-	-	79.55^**	[<0.001]	38.29^**	[<0.001]
Male	1.63^*	(1.50–1.77)	2.78^*	(2.40–3.23)	1.64^*	(1.24–2.16)
χ²₁ [p]	133.29^**	[<0.001]	187.69^**	[<0.001]	12.67^**	[<0.001]
Percentage of individual’s age cohort already using⁵	1.34^*	(1.30–1.39)	1.37^*	(1.30–1.45)	1.76^*	(1.51–2.05)
χ²₁ [p]	328.90^**	[<0.001]	135.30^**	[<0.001]	53.95^**	[<0.001]
Education⁶
Student	1.53	(0.96–2.45)	2.02^*	(1.39–2.93)	0.66	(0.31–1.40)
Low	1.25	(0.81–1.90)	1.88^*	(1.39–2.56)	0.76	(0.38–1.52)
Low/Med	0.69	(0.46–1.06)	1.52^*	(1.03–2.24)	0.65	(0.33–1.29)
Med/High	1.18	(0.76–1.83)	1.76^*	(1.27–2.44)	0.75	(0.39–1.44)
High	1.00	-	1.00	-	1.00	-
χ²₄ [p]	37.91^**	[<0.001]	18.07^**	[0.001]	2.07	[0.723]

Cannabis	*N=8,463*		*N=1,599*⁷		*N=1,604*⁷

Individual’s age of commencing cannabis use⁴
Early youth	-	-	0.61^*	(0.37–1.00)	1.06	(0.58–1.95)
Mid-teens	-	-	0.71	(0.42–1.22)	0.59	(0.33–1.06)
Adulthood	-	-	1.00	-	1.00	-
χ²₂ [p]	-	-	3.97	[0.137]	8.74^**	[0.013]
Male	1.94^*	(1.70–2.21)	1.55^*	(1.20–2.00)	1.69^*	(1.03–2.78)
χ²₁ [p]	102.81^**	[<0.001]	12.04^**	[0.001]	4.49^**	[0.034]
Percentage of individual’s age cohort engaged in use⁵	2.09^*	(1.88–2.33)	1.17	(0.95–1.44)	2.57^*	(1.60–4.13)
χ²₁[p]	182.19^**	[<0.001]	2.25	[0.134]	15.75^**	[<0.001]
Education⁶
Student	2.36^*	(1.66–3.36)	1.94	(0.97–3.89)	1.24	(0.32–4.77)
Low	1.42	(0.95–2.10)	2.20^*	(1.19–4.08)	1.43	(0.42–4.86)
Low/Med	1.35	(0.87–2.08)	0.84	(0.37–1.91)	1.44	(0.39–5.37)
Med/High	0.97	(0.63–1.49)	1.56	(0.80–3.05)	1.28	(0.35–4.72)
High	1.00	-	1.00	-	1.00	-
χ²₄[p]	61.09^**	[<0.001]	13.54^**	[0.009]	0.56	[0.967]

Person-years were defined from six years of age for alcohol and thirteen years of age for cannabis in modelling commencement of use.

^1.

N = The total unweighted number of respondents included in model, conditioning on initial stage.

^2.

Model also controlled for age person year (not shown in table) - groups were <= 14, 15–17, 18–20, 21–24, 25–29, and 30+.

^3.

Individual’s age of commencing alcohol use is split into tertiles among all those who ever used alcohol. The earliest (early youth) tertile is age <=15, the 2^nd tertile (mid-teens) age 16–17 and the 3^rd tertile (adulthood) aged 18+.

^4.

Individual’s age of commencing cannabis use is split into tertiles among those who ever used cannabis. The first tertile (early youth) is age <=16, the 2^nd tertile (mid-teens) 17–18 and the last (adulthood) 19+.

^5.

%(/10) of +/−5-yr cohort used by prior person year. e.g. For an individual born in 1975 the cohort would be persons born between 1970 and 1980. An OR of 1.5 for commencement of use would be interpreted as an increase of 50% in the odds of commencing use with an increase of 10% of people in the age cohort who had commenced use by the previous person year (controlling for all other variables in the model).

^6.

Low education is defined as completed 11 or less years, low/med is completed 12 years, medium 13–15 years and high 16 or more years.

Individuals with a missing age of onset were excluded from the model (N=4 for cannabis abuse and N=2 for cannabis dependence).

^*/**

- significant at the 0.05 level, two-sided test; CI, confidence interval; OR, odds ratio.