Do drug treatment variables predict cognitive performance in multidrug-treated opioid-dependent patients? A regression analysis study

Table 5 Hierarchical regression results for verbal memory (n = 74)

Predictors in the reduced model	Step 1 Beta (t-test)^a	Step 2 Beta (t-test)	Step 3 Beta (t-test)	Step 4 Beta (t-test)	Step 5 Beta (t-test)
Substance abuse variable
Frequency of the previous month substance abuse (high vs. low)^b	-.35	-.34 **	-.36 **	-.35 **	-.36 **
	t(72) = 3.17	t(71) = 3.24	t(70) = 3.34	t(69) = 3.22	t(68) = 3.15
	p = 0.002**	p = 0.002**	p = 0.0013**	p = 0.002**	p = 0.002**
Drug treatment variables
The number of psychoactive drugs, other than opioid or BZD (high vs. low)^c		-.32	-.35	-.35	-.35 **
		t(71) = 3.06	t(70) = 3.15	t(69) = 3.13	t 68) = 2.99
		p = 0.003**	p = 0.002**	p = 0.003**	p = 0.004**
BZD treatment (yes vs. no)			.10	.10	10
OST drug type (buprenorphine vs. methadone)				-.03	-.03
Duration of OST (long vs. short)^d					.01
R² (adjusted)	.110	.203	.199	.189	.177
Model (ANOVA)	F(1,72) = 10.02	F(2,71) = 10.28	F(3,70) = 7.06	F(4,69) = 5.24	F(5,68) = 4.14
Model (ANOVA)	p = 0.002**	p = 0.0001***	p = 0.0003 ***	p =0.001***	p =0.002 *
Change (ANOVA)^a		F(1,71) = 9.37
Change (ANOVA)^a		p = 0.003 **	p = 0.40	p = 0.79	p = 0.91

^aOnly p-value shown when p ≥ 0.10.
^bConsidered as high when three or more days a week. Alcohol use was taken into account if it was at least mean weekly 16 portions (12 g) for females and 24 portions for males or binge drinking occurred on any day.
^cConsidered as low up to one drug.
^dConsidered as short when between six and twelve months.
***p <0.001. **p < 0. 01. *p < 0.05. #p < 0.10.

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