Summary assessment of the overall risk of bias—Cochrane Collaboration’s tool
| Study | Different types of bias | Summary within study | Overall risk | ||||||
| 1 | 2 | 3 | 4 | 5 | 6 | ||||
| 1 | Benjaminse et al, 201529 | U | U | H | U | L | L | H=1 L=2 U=3 | Enrolment, allocation and testing done by the same person. Lack of information in terms of selection and attrition |
| 2 | Gokeler et al, 201528 | L | L | U | L | L | L | H=0 L=5 U=1 | Lack of information in terms of blinding |
| 3 | Laufer et al, 200723 | U | U | U | L | L | L | H=0 L=3 U=3 | Lack of information in terms of selection bias and blinding |
| 4 | Prapavessis and McNair, 199924 | L | U | U | L | L | L | H=0 L=4 U=2 | Allocation concealment not reported. Lack of information in terms of blinding |
| 5 | Rotem-Lehrer and Laufer, 200725 | U | U | U | L | L | H=0 L=3 U=3 | Lack of information in terms of selection bias and blinding | |
| 6 | Weilbrenner, 201426 | L | U | U | L | L | L | H=0 L=4 U=2 | Allocation concealment and blinding not reported |
Risk of bias criteria: 1, selection bias=random sequence generation; 2, selection bias=allocation concealment; 3, performance bias/detection bias=blinding of personnel and blinding of participants/blinding of outcome assessors; 4, attrition bias=incomplete outcome data; 5, reporting bias=short-term selective outcome reporting; 6, other bias=potential threats to validity, for example, consideration of a protocol. Levels of risk of bias: H, high risk of bias; L, low risk of bias and U, unclear risk of bias.