Methadone vs. buprenorphine/naloxone during early opioid substitution treatment: a naturalistic comparison of cognitive performance relative to healthy controls

Table 1 Group demographics

	Methadone (n = 16)	Buprenorphine/Naloxone (n = 17)	Control (n = 17)	Group comparison p-values
Age, years (M, SD)	30.8 (8.8)	28.1 (6.3)	31.1 (11.2)	ns
Sex: females/males	9/7	7/10	9/8	ns
Verbal intelligence ^a (M, SD)	98.4 (8.7)	102.4 (8.4)	105.4 (9.8)	C > M*
Education, years (M, SD)	10.4 (2.0)	11.1 (2.2)	13,0 (1.7)	C > M C > BN
Dependencies
Opioid	100%	100%	-	ns ^b
Alcohol	0%	6%		ns ^b
Amphetamine	0%	11%		ns ^b
Benzodiazepines	100%	89%		ns ^b
Cannabis	6%	11%		ns ^b
Main opioid of abuse used within last month (%)
Buprenorphine	75%	100%	-	ns ^b
Heroin	13%	0%		ns ^b
Methadone	13%	0%		ns ^b
Other substances of abuse used within last month (%)
Alcohol (heavy use)^c	6%	17%	6%	ns
Amphetamine	19%	29%	0%	ns
Benzodiazepine^d	94%	94%	0%	M & BN > C**
Cannabis	38%	24%	0%	M > C*
Nicotine (daily use)	100%	100%	35%	M & BN > C**
Duration of opioid substitution treatment in the day of testing, days (M, SD)	14.3 (7.4)	11.0 (8.1)	-	ns ^b
Duration of opioid abuse, years (M, SD)	12.1 (7.7)	10.0 (3.5)	-	ns ^b
Duration of any substance abuse, years (M, SD)	16.9 (8.7)	15.7 (5.0)	-	ns ^b

^aEstimation based on WAIS-R Vocabulary score.
^bTested only between methadone- and buprenorphine/naloxone-treated patients.
^cAlcohol use was considered heavy if it was at least mean weekly 16 portions (12 g) for females and 24 weekly portions for males.
^dIncludes benzodiazepines used on prescription.
M = methadone, BN = buprenorphine/naloxone
> = superior than, *** = statistically significant at level p < 0.001. ** = statistically significant at level p < 0.01. * = statistically significant at level p < 0.05.