Table 2.

Assessment of bias for each study, using the Cochrane Collaboration's tool for assessing risk of bias for randomised studies and the ROBINS-I bias tool for observational studies

Randomised studies
Author [ref]	Sequence generation	Allocation concealment	Blinding	Incomplete outcome reporting	Selective outcome reporting	Other potential threats to validity	Overall rating of bias
Bonkovsky [40]	Unclear	Unclear	No	Yes	Yes	Unclear	Unclear
Bruce [41]	Unclear	Unclear	No	Yes	Yes	Unclear	Unclear
Hilsden [42]	Yes	Unclear	No	No	Unclear	Unclear	Unclear
Litwin [43]	Unclear	Unclear	Unclear	Unclear	Unclear	Unclear	Unclear

Observational studies
Author [ref]	Confounding	Selection of participants into the study	Classification of interventions	Deviations from intended intervention	Missing data	Measurement of outcomes	Selection of the reported result	Overall rating of bias
Cioe [19]	Moderate	Moderate	Moderate	Moderate	Low	Moderate	Low	Moderate
Nosotti [27]	Serious	Critical	Moderate	Serious	Serious	Serious	Serious	Critical