Table 1.

Moderators of the effectiveness of ACT Interventions for Undergraduate Students

Moderator Variables	k	#ES	B0/g	t0	B1	t1	F(df1, df2)	p-value
Intervention Characteristics
Treatment Focus							F(1, 54) = 4.09	.048
Non-Clinical (RC)	20	56	0.20	1.65
Clinical	20	56	0.53	4.71**	−.33	−2.02*
Control Group Type							F (1, 54) = 2.76	.10
Waitlist/No Treatment (RC)	20	56	0.48	4.66**
Active Control	20	56	0.25	2.25**	.22	1.66
Intervention Size							F (1, 54) = 2.23	.14
Individual (RC)	20	56	0.29	2.80**
Group	20	56	0.57	3.66**	−.28	−1.49
Delivery Modality							F (2, 53) = 1.11	.34
In-Person (RC)	20	56	0.50	4.00**
Online	20	56	0.30	1.95	−.20	−.99
Bibliotherapy	20	56	0.16	0.72	−.34	−1.36
Number of Sessions							F (1, 54) = 2.42	.13
Single (RC)	20	56	0.04	0.16
Multiple	20	56	0.43	4.26**	.39	1.55
Outcome Measure							F (1, 54) = 3.02	.08
AAQ-II and Derivatives (RC)	20	56	0.33	3.51**
Not AAQ-II and Derivatives	20	56	0.46	4.44**	.12	1.74
Outcome Assessed							F (1, 54) = 1.08	.30
Psychological Flexibility (RC)	20	56	0.44	4.10**
Psychological Inflexibility	20	56	0.36	3.99**	−.08	−1.04
Timepoint							F (1, 48) = 2.61	.09
Post-Intervention	20	56	0.41	4.57**
Follow-up	20	56	0.29	2.88*	−.12	−1.73
Length of Follow-Up (in months)	19	9	0.28	2.11*	.05	.96	F (1, 17) = 0.93	.35
Participant Characteristics
Participant Age	20	56	0.37	3.85**	−.01	−.41	F (1, 54) = 0.16	.69
Percentage Female	20	56	0.39	5.06**	−.01	−2.48*	F (1, 54) = 6.15	.02
Participant Race
% White	13	39	0.33	2.73**	−.01	−1.07	F (1, 37) = 1.15	.29
% Black or African American	13	39	0.25	2.50*	.01	1.49	F (1, 37) = 2.22	.14
% Native American or Alaskan Native	13	39	0.27	2.35*	.002	0.05	F (1, 37) = .003	.96
% Asian	13	39	0.23	0.60	−.003	0.90	F (1, 37) = 0.02	.90
% Native Hawaiian or Pacific Islander	13	39	0.29	2.48*	−.06	−.52	F (1, 37) = 0.27	.61
% Multiracial or Other	13	39	0.31	2.98**	−.05	−1.52	F (1, 37) = 2.30	.14

Note.

k = number of independent studies; #ES = number of effect sizes; B₀/g = intercept or mean effect size; t₀ = test of whether the mean effect size significantly deviates from zero; B₁ = estimated unstandardized regression coefficient; t₁ = test of difference in mean effect size with reference category; F (df1, df2) omnibus test of moderation; RC = Reference category.

For categorical moderators, each intercept represents the mean effect of a category, and each slope represents the difference in the mean effect between the category and reference category. Therefore, the slope of the reference category is not reported because it represents a comparison of the reference category with itself. The slope of a continuous moderator represents an increase or decrease in effect size with each unit increase in the variable.

^*p < .05;

^**p < .01.