Table 1.

Effect of group cognitive behavioral therapy versus usual care on outcomes

	Intervention effect at:			Variance components for random effects:
	3 months	6 months	LLstat (2 df)	Intercept (client)	Session	Residual
Mental health outcomes
Change in Beck Depression Inventory-II score	-6.3****	-5.6***	16.3***	64.2****	106.2	72.3****
Change in Short Form-12 version 2 mental health score	6.3***	4.6**	16.3***	47.7****	94.3	92.2****
Substance use outcomes
Change in percent of days used alcohol on days available for clients with at least one day available to use, past 30 days	n/a	-8.9*	n/a	n/a	0	800.6****
Change in percent of days used problem substance on days available for clients with at least one day available to use, past 30 days	n/a	-11.6*	n/a	n/a	0	975.3****

^****p<0.0001;

^***p<0.001;

^**p<0.01;

^*p<0.05.

LLstat: log-likelihood ratio statistic for testing the total intervention effect for outcomes examined at 3- and 6-months.