Table 3.

Effect sizes (d) of Within and Between Subject Effects for Primary Outcomes

Outcomes:	ACT	CBT	Between Groups		ACT	CBT
Anxiety Specific
CSR
Linear Pre-Post	−3.74	−3.46	0.26	Quadratic: β	0.71	0.73
Linear Post-FU	−1.98	−1.78	0.32	Quadratic: effect size (d)	0.82	0.84
Linear 6–12m FU	−0.46	−0.08	0.38
ASI
Linear Pre-Post	−1.18	−0.63	0.55	Quadratic: β	3.08	1.39
Linear Post-FU	−0.65	−0.39	0.26	Quadratic: effect size (d)	0.26	0.12
Linear 6–12m FU	−0.12	−0.15	0.03
PSWQ
Linear Pre-Post	−0.74	−0.64	0.11	Quadratic: β	2.00	1.64
Linear Post-FU	−0.40	−0.36	0.05	Quadratic: effect size (d)	0.17	0.14
Linear 6–12m FU	−0.06	−0.07	0.02
FQ
Linear Pre-Post	−0.83	−0.52	0.31	Quadratic: β	0.34	0.61
Linear Post-FU	−0.38	−0.27	0.11	Quadratic: effect size (d)	0.13	0.22
Linear 6–12m FU	0.06	−0.02	0.08
Non-Anxiety Specific
AAQ (higher scores indicate improvement)
Linear Pre-Post	1.16	0.90	0.26	Quadratic: β	−3.20	−2.70
Linear Post-FU	0.63	0.45	0.18	Quadratic: effect size (d)	−0.27	−0.22
Linear 6–12m FU	0.10	0.00	0.10
QOLI (higher scores indicate improvement)
Linear Pre-Post	0.43	0.43	0.00	Quadratic: β	−0.15	−0.21
Linear Post-FU	0.21	0.26	0.06	Quadratic: effect size (d)	−0.08	−0.11
Linear 6–12m FU	0.00	0.12	0.12

Notes: For the sake of clarity, effect sizes reflect HLM models with linear and quadratic time terms only. Quadratic terms are invariant across assessment points.

CSR = ADIS-IV principal disorder clinical severity ratings; ASI = Anxiety Sensitivity Index; PSWQ = Penn State Worry Questionnaire; FQ = Main Target Phobia Scale (behavioral avoidance rating) from the Fear Questionnaire; AAQ = Acceptance and Action Questionnaire; QOLI = Quality of Life Inventory