Table 3.

Study-level moderators of substance-use outcomes (n = 53)

Model	β	b	z	p
Client factors
Biological outcome	−.191	−.118	−1.87	.061
6- to 12-month outcome	−.170	−.102	−1.63	.104
Mean age of participants	−.071	−.004	−0.58	.560
Percentage female participants	.248	.005	2.66	.008
Co-occurring disorder inclusion	−.046	−.028	−0.44	.659
Illicit drug outcome	.123	.073	0.98	.327
R2 = .186
QE (46) = 104.86§
Treatment factors
Biological outcome	−.129	−.079	−1.16	.247
6- to 12-month follow-up outcome	−.228	−.134	−2.23	.026
Treatment delivery	.152	.096	1.61	.108
Treatment format	.017	.011	0.17	.866
Treatment length	−.312	−.008	−3.00	.003
R2 = .193
QE (47) = 103.52§
Final model–weighted least squaresa
Biological outcome	−.083	−.050	−0.78	.432
6 to 12-month follow-up outcome	−.261	−.153	−2.57	.010
Percentage female participants	.200	.004	2.06	.039
Treatment length	−.252	−.006	−2.47	.014
R2 = .205
QR (4) = 26.25§
QE (48) = 101.95§
g = 0.144§
Final model-maximum likelihood
Biological outcome	−.048	−.037	−0.34	.732
6- to 12- month follow-up outcome	−.185	−.134	−1.44	.149
Percentage female participants	.226	.004	1.69	0.89
Treatment length	−.259	−.007	−1.76	.077
R2 = .169
QR (4) = 10.90*
QE (47) = 53.52
τ2 = .04
g = 0.155§

Notes: Attrition rate nonsignificant as a methodological covariate.

^aResults held in the final weighted least squares model with the two high-weight trials (Project MATCH, 1997; Anton et al., 2006) removed.

^* p <.05;

^§ p <.005.