Table 2 Randomized study quality indicators

Dwight-Johnson et al. (2011) [54]

Yes: Stratified permuted-block randomization

Participants: No

Intervention: 16%

Intent-to-treat analysis (ITT) employed

No power calculation

ITT can increase chance of false positive

Researchers: No

Control: 30%

Outcome Assessor: Yes

Ueberlacker et al. (2011) [62]

Yes: method not described

Participants: No

Intervention: 26%

Not described in detail, but it appears that missing data points have been excluded.

Small sample, risk of attrition bias

Researchers: No

Control: 42%

No power calculation

Outcome Assessor: Yes

Yeung et al. (2010) [64]

Yes: computer-generated table

Participants: No

Not reported

Not reported

No power calculation

Researchers: No

Outcome Assessor: Yes

Yeung et al. (2012) [63]

Yes: randomized using computer-generated numbers

Participants: No

Intervention: 27%

Used data from week 6 if no data available at week 12. If neither data point available participant was excluded from analysis

Power calculation suggest much larger sample is required

Researchers: No

Control: 15%

Outcome Assessor: Yes

Choi et al. (2012) [53]

Yes: randomization process by independent person

Participants: No

Intervention: 34%

Baseline carried forward

The missing data approach may introduce false positives. No power calculation Small sample

Researchers: No

Control: 10%

Outcome Assessor: No

Beeber et al. (2010) [51]

Yes: block randomization

Participants: No

Intervention: 13%

Power calculation completed and extra participants included to compensate for possible attrition

Small sample

Researchers: No Outcome Assessor: No

Control: 10%

Renner et al. (2011) [59]

Yes: method not described

Participants: Not reported

Intervention CBT: 52%

Non-completers excluded

Small sample high risk of attrition bias

Researchers: Not reported

Intervention SHG: 28%

Potential risk of selection bias

Outcome Assessor: Not reported

Control: 45%

No power calculation