Table 2. Comparisons in addiction-related issues between the two groups.

Dimension	Time period*	MMT+CM group	MMT group	All subjects	Statistical analysis GEE: F, P
					Temporal main effects	Main effects of CM intervention	Interaction of time and CM intervention
Self-report of heroin use in 30 days prior to interview** Mean (SD) days	Baseline	26.5(7.1)	24.6(9.3)	25.5(8.3)	1144.51	0.79	0.57
	4 weeks	0.9(3.7)	2.2(6.8)	1.6(5.5)	<0.001	0.375	0.449
	12 weeks	1.3(5.8)	0.9(4.5)	1.1(5.1)
	24 weeks	0.3(1.7)	0.2(1.0)	0.2(1.4)
Physical condition dimension score Mean (SE of mean)	Baseline	0.14(0.02)	0.15(0.02)	0.15(0.02)	7.15	0.01	0.00
	4 weeks	0.07(0.02)	0.09(0.02)	0.08(0.02)	0.008	0.911	0.983
	12 weeks	0.10(0.02)	0.08(0.02)	0.09(0.02)
	24 weeks	0.07(0.03)	0.09(0.03)	0.08(0.02)
Employment dimension score Mean (SE of mean)	Baseline	0.57(0.02)	0.56(0.03)	0.57(0.02)	12.32	0.88	0.32
	4 weeks	0.53(0.03)	0.59(0.03)	0.56(0.02)	<0.001	0.350	0.569
	12 weeks	0.50(0.03)	0.55(0.03)	0.52(0.02)
	24 weeks	0.51(0.03)	0.48(0.04)	0.49(0.02)
Alcohol problem dimension score Mean (SE of mean)	Baseline	0.03(0.01)	0.03(0.01)	0.03(0.01)	2.00	1.77	1.57
	4 weeks	0.02(0.01)	0.02(0.01)	0.02(0.00)	0.158	0.183	0.210
	12 weeks	0.01(0.01)	0.01(0.00)	0.01(0.00)
	24 weeks	0.02(0.01)	0.02(0.01)	0.02(0.01)
Drug problem dimension score Mean (SE of mean)	Baseline	0.16(0.01)	0.15(0.01)	0.15(0.01)	243.27	0.56	1.16
	4 weeks	0.08(0.01)	0.08(0.01)	0.08(0.01)	<0.001	0.453	0.282
	12 weeks	0.05(0.01)	0.05(0.01)	0.05(0.01)
	24 weeks	0.03(0.01)	0.05(0.01)	0.04(0.01)
Legal problems dimension score Mean (SE of mean)	Baseline	0.15(0.01)	0.16(0.01)	0.16(0.01)	21.01	0.00	0.01
	4 weeks	0.09(0.01)	0.08(0.01)	0.08(0.01)	<0.001	0.959	0.931
	12 weeks	0.11(0.01)	0.11(0.01)	0.11(0.01)
	24 weeks	0.10(0.01)	0.09(0.01)	0.10(0.01)
Family status dimension score Mean (SE of mean)	Baseline	0.14(0.02)	0.15(0.02)	0.14(0.01)	33.49	0.68	0.00
	4 weeks	0.05(0.01)	0.09(0.01)	0.07(0.01)	<0.001	0.410	0.966
	12 weeks	0.05(0.01)	0.09(0.01)	0.07(0.01)
	24 weeks	0.05(0.01)	0.06(0.01)	0.05(0.01)
Mental health dimension score Mean (SE of mean)	Baseline	0.06(0.01)	0.08(0.02)	0.07(0.01)	10.31	0.88	0.49
	4 weeks	0.02(0.01)	0.02(0.01)	0.02(0.00)	0.001	0.349	0.484
	12 weeks	0.02(0.01)	0.04(0.01)	0.03(0.01)
	24 weeks	0.03(0.02)	0.02(0.01)	0.02(0.01)

MMT=Methadone Maintenance Treatment; CM=Contingency Management; SD=Standard Deviation; SE=Standard Error

*160 subjects participated in the baseline evaluation (80 in each group); 151 subjects participated in the 4-week evaluation (75 in the MMT+CM group, 76 in the MMT group); 139 subjects participated in the 12-week evaluation (70 in the MMT+CM group and 69 in the MMT group); and 125 subjects participated in the 24-week evaluation (63 in the MMT+CM group and 62 in the MMT group).

** Self-report of heroin use in 30 days prior to interview is one item in the ‘Drug problem’ dimension