Author & year	1.1 question	1.2 random	3 concealment	4 double-blind	5 similar group	6 controlled	7 standard outcome measure	8 attrition rate	9 ITT (Intention-to-Treat analysis)	10 multiple site equiv.	2.1 overall
Note. Full description of quality checklist questions can be found in Appendix B. Abbreviations: equiv. = equivalent; sig. = significant; expr = experimental. Key for rating: 1 = Well covered; 2 = Adequately addressed; 3 = Poorly addressed; N/A = Not addressed/not applicable; ++ = all or most of the criteria fulfilled (unfulfilled criteria very unlikely to alter conclusions of study); + = some of the criteria fulfilled (unfulfilled criteria unlikely to alter conclusions of study).
Abrams & Siegal (1), 1978	1	1	N/A	N/A	1	1	1	27%	1	1	+
Abrams & Siegal (2), 1978	1	1	N/A	N/A	1	1	1	17%	1	1	+
Ahrens & Rexford, 2002	1	1	N/A	N/A	2	1	1	0% (not explicitly stated)	1	1	+
Biggam & Power, 2002	1	1	2	2	1	2	1	41%	1	1	+
Bilderbeck, 2013	1	1	N/A	N/A	1	1	1	31%	N/A	1	+
Bradley & Follingstad, 2003	1	1	N/A	N/A	1	1	1	37%	1	1	+
Chandiramani, 1995	1	2	N/A	N/A	2–more illiterate in experimental group	2	1	0% (not explicitly stated)	1	1	+
Chen, 2015	1	1	1	N/A	1	1	1	8%	1	1	+
Cole, 2007	1	1	N/A	N/A	1	3–higher baselines in expr (effect on small sample size)	1	31%	1	1	+
Ford, 2013	1	1	1	1	1	1	1	10%	2	1	++
Gold, 2014	1	1	N/A	N/A	1	1	1	39%	1	1	+
Gussak (1), 2009	1	1	N/A	N/A	1	1	1	48%	N/A	1	+
Gussak (2), 2009	1	1	N/A	N/A	1	1	1	24%	N/A	1	+
Gussak, 2007a	1	1	2	2	3–at beginning of experiment: BDI score higher in expr group)	3	1	41%	1	1	+
Hilkey et al., 1982	1	1	N/A	2	2	1	1	0%	1	1	+
Johnson & Zlotnick, 2012	1	1	1	1	1	1	1	11%	1	1	++
Khodayarifard (1), 2010	1	1	N/A	N/A	1	1	1	28%	N/A	1	+
Khodayarifard (2), 2010	1	1	N/A	N/A	1	1	1	27%	N/A	1	+
Loper & Tuerk, 2011	1	1	N/A	N/A	1	2	1	18%	1	1	+
Maunder, 2009	1	1	1	1–blind researcher	1	1	1	50%	1	1–pilot study	+
Messina, 2010	1	1	1	N/A	1	1	1	18%	1	1	++
Mitchell, 2011	1	1	1	1	1	1	1	5%	1	1	++
Pardini (1), 2014	1	1	1	N/A	1	1	1	38%	1	1–pilot study	+
Pardini (2), 2014	1	1	1	1–blind researcher	1	1	1	17%	1	1	++
Perkins, 1998	1	1	N/A	N/A	1	1	1	10%: 15 drop out; other attrition due to transfers, WRIT, release	N/A	1	+
Richards, 2000	1	1	N/A	N/A	1	1	1	7%	N/A	1	+
Rohde, 2004	1	1	N/A	N/A	2	2	1	0%	1	1	+
Sleed, 2013	1	1	1	1	2	1	1	29%	1	1	++
Sumter, 2009	1	1	N/A	N/A	1	1	3	0% (not explicitly stated)	1	1	+
Valentine & Smith, 2001	1	1	2	N/A	1	1	1	17%	1	1	++
Villagra Lanza (1), 2014	1	1	N/A	N	2	2	1	19% at follow-up; 0% at post-test	1	1	+
Villagra Lanza (2), 2014	1	1	N/A	N/A	1	1	1	3%	1	1	+
Wilson, 1990	1	1	2	N/A–same therapist for all conditions	1	1	1	0%	1	1	+
Wolff (1), 2015	1	2–random & preference groups; no sig. difference between two groups	N/A	N/A	1	2	1	13%	1	1	+
Wolff (2), 2015	1	2–random & preference groups; no sig. difference between two groups	N/A	N/A	1	2	1	10%	1	1	+
Zlotnick, 2002	1	1	N/A	N/A	1	1	1	0%	N/A	1	+
Zlotnick, 2009	1	1	N/A	N/A	1	1	1	10%	1	1	+