A total of 8 studies met our criteria for elevated levels of depressive symptoms at pre-treatment: four studies in populations with pain (Lush et al., 2009; Sagula & Rice, 2004; Sephton et al., 2007; Rosenzweig et al., 2009), two studies in populations with other medical problems (Bedard et al., 2003; Reibel, Greeson, Brainard, & Rosenzweig, 2001), one study using a sample with Binge Eating Disorder (Kristeller & Hallett, 1999), and one study using a sample with ADHD (Zylowska et al., 2008). The average pre-post effect size estimate (Hedges’ g) based on these studies was 0.53 (95% CI: 0.44-0.61, p < .01). The fail-safe N was 296 (z-value = 12.08), indicating that these results are also robust. The average pre-post effect size estimate (Hedges’ g) for the 16 studies that did not have elevated levels of depressive symptoms at pre-treatment was 0.50 (95% CI: 0.39-0.61, p < .01). This result was also robust (fail-safe N = 667; z-value = 12.80).
