There was an effect for cohort within both arms of the study, necessitating a nested analysis. Because a fully nested MMRM analysis did not converge, an aggregate repeated measures ANCOVA was applied and showed no effect for treatment condition (p = .30), a significant effect for time (p = .011), and a significant and large interaction of condition and time, F(1, 13) = 6.33, p = .026, partial η2 = .33. Control participants showed no significant improvement from pre- to posttreatment (note, in interpreting these values, that lower scores mean greater social support), Mdiff = −1.24, SE = 1.57, t(124.40) = −0.795, p = .428, 95% CI [−4.36, 1.86], effect size = .10, or pretreatment to follow-up, Mdiff = −1.70, SE = 2.52, t(91.58) = −0.675, p = .50, 95% CI [−6.70, 3.31], effect size = .11. Participants in the ACT condition also showed no significant improvement from pre- to posttreatment, Mdiff = −1.93, SE = 1.50, t(120.11) = −1.28, p = .202, 95% CI [−4.91, 1.405], effect size = .16, but significant improvement during the follow-up period, Mdiff = −7.11, SE = 2.56, t(91.88) = −2.78, p = .007, 95% CI [−12.19, −2.03], effect size = .42.
