TABLE 4.

Effects of Substance-Use Disorders, by Poverty and Test for Differential Effects: National Epidemiologic Survey on Alcohol and Related Conditions, United States, 2001–2005

	Effect When Not in Poverty		Effect When in Poverty		Differential Effecta of AUD/DUD When in Poverty
Variable	RD % (SE)	P	RD % (SE)	P	IC % (SE)	P
Unadjustedb (Ref = neither disorder)
Alcohol-use disorder only	2.9 (0.7)	<.001	12.1 (3.1)	<.001	9.2 (3.2)	.005
Drug-use disorder only	9.1 (3.0)	.004	28.1 (8.0)	<.001	19.0 (8.4)	.028
Both alcohol- and drug-use disorder	10.0 (3.2)	.003	14.5 (6.4)	.027	4.5 (6.6)	.499
Adjustedc (Ref = neither disorder)
Alcohol-use disorder only	0.6 (0.5)	.257	3.6 (1.5)	.017	3.1 (1.6)	.052
Drug-use disorder only	3.0 (1.8)	.092	11.4 (5.2)	.03	8.8 (5.4)	.112
Both alcohol- and drug-use disorder	2.0 (1.6)	.233	2.2 (2.7)	.424	0.3 (3.0)	.918

Note. AUD/DUD = alcohol-use disorder/drug-use disorder; IC = interaction contrast; RD = risk difference.

^aDifferential effect (i.e., IC) is the difference in RD (e.g., 9.2 = 12.1 - 2.9).

^bUnadjusted effects can be obtained by taking differences in incidence rates in Table 2.

^cAdjusted effects represent expected risk differences if each AUD/DUD by poverty strata was fixed to have all of the control variables to be equal.