An MMRM analysis that nested participants within cohorts did not converge, but there was no effect for cohort or the Cohort × Time interaction for either arm of the study (p = .5); thus, a nonnested analysis was conducted. The analysis showed no effect for treatment condition (p = .73), but there was a significant effect for time (p < .001) and the interaction of condition and time, F(1, 103.2) = 3.60, p = .031, effect size = .36. The interaction occurred because the control participants showed a medium and significant improvement from pre- to posttreatment, Mdiff = 5.01, SE = 0.95, t(125.03) = 5.24, p < .001, 95% CI [3.12, 6.90], effect size = .69, but no change (now in the direction of deterioration) from pretreatment to follow-up, Mdiff = −0.16, SE = 1.41, t(98.73) = −0.11, p = .91, 95% CI [−2.95, 2.63], effect size = −.02. Participants in the ACT condition also showed a medium and significant improvement from pre- to posttreatment, Mdiff = 4.26, SE = 0.92, t(121.93) = 4.64, p < .001, 95% CI [2.44,
