Table 2.

Further exploration of patterns of use of five drugs over a 10 year period: relationships of levels of use at each year¹

	Primary Drug²
Time-dependent covariate (i.e. level of non-primary substance use at each time period)³	Heroin (N=629)	Cocaine (N=694)	Methamphetamine (N=474)
Year 1
Heroin	--	−0.05	0.30
Cocaine	0.13	--	−0.07
Methamphetamine	0.06	0.06	--
Marijuana	−0.12^*	−0.09^*	0.21^*
Alcohol	−0.01	0.22^*	0.22^*
Year 2
Heroin	--	0.08	0.40
Cocaine	0.18	--	−0.10
Methamphetamine	0.07	0.01	--
Marijuana	−0.04	−0.08^*	0.23^*
Alcohol	0.01	0.23^*	0.23^*
Year 3
Heroin	--	0.10	0.16
Cocaine	0.09	--	−0.15
Methamphetamine	0.09	−0.09	--
Marijuana	−0.04	−0.02	0.26^*
Alcohol	0.07	0.23^*	0.28^*
Year 4
Heroin	--	0.19	0.04
Cocaine	0.44^*	--	−0.13
Methamphetamine	0.10	−0.26	--
Marijuana	−0.01	−0.01	0.27^*
Alcohol	0.14	0.27^*	0.29^*
Year 5
Heroin	--	0.20	0.13
Cocaine	0.31	--	−0.10
Methamphetamine	−0.03	−0.24^*	--
Marijuana	0.04	0.02	0.27^*
Alcohol	0.21^*	0.32^*	0.27^*
Year 6
Heroin	--	0.35^*	0.10
Cocaine	0.40^*	--	−0.07
Methamphetamine	−0.19	−0.24	--
Marijuana	0.06	0.08^*	0.32^*
Alcohol	0.25^*	0.34^*	0.27^^
Year 7
Heroin	--	0.35^*	0.09
Cocaine	0.34^*	--	−0.04
Methamphetamine	−0.16	−0.23^*	--
Marijuana	0.05	0.09^*	0.29^*
Alcohol	0.27^*	0.37^*	0.30^*
Year 8
Heroin	--	0.49^*	0.05
Cocaine	0.53^*	--	0.02
Methamphetamine	−0.10	−0.05	--
Marijuana	0.10	0.07	0.37^*
Alcohol	0.22^*	0.38^*	0.27^*
Year 9
Heroin	--	0.41^*	0.07
Cocaine	0.01	--	0.01
Methamphetamine	−0.07	−0.10	--
Marijuana	0.15^*	0.06	0.36^*
Alcohol	0.22^*	0.40^*	0.31^*
Year 10
Heroin	--	0.28	−0.06
Cocaine	−0.11	--	−0.12
Methamphetamine	0.14	−0.31	--
Marijuana	0.11	0.08	0.39^*
Alcohol	0.33^*	0.38^*	0.32^*

p<.01

Results are from three growth models; parameters included random intercept and slope of primary drug over time and levels of use of non-primary substances as time-dependent covariates.

Each column represents a separate analysis (of the specified primary drug subsample).

Results in the table are estimates of parameters for each time period and indicate the relationship of the level of use of the primary drug to that of each of the non-primary drugs. Note that for simplicity, other parameters in the models are not shown in table (intercept, slope, variance, covariance).