Selection bias
Random sequence generation	Low risk of bias	The investigators describe a random component in the sequence generation process, such as: referring to a random number table; using a computer random number generator; coin tossing; shuffling cards or envelopes; throwing dice; drawing of lots; or minimisation.
	High risk of bias	The investigators describe a non‐random component in the sequence generation process, such as: sequence generated by odd or even date of birth; sequence generated by some rule based on date (or day) of admission; or sequence generated by some rule based on hospital or clinic record number. The investigators describe other non‐random approaches, such as: allocation by judgement of the clinician; allocation by preference of the participant; allocation based on the results of a laboratory test or a series of tests; or allocation by availability of the intervention.
	Unclear risk of bias	There is insufficient information about the sequence generation process to permit a judgement of low or high risk of bias.
Allocation concealment	Low risk of bias	Participants and investigators enrolling participants could not foresee assignment because one of the following, or an equivalent method, was used to conceal allocation: central allocation (including telephone, web‐based, and pharmacy‐controlled randomisation); sequentially numbered drug containers of identical appearance; or sequentially numbered, opaque, sealed envelopes.
	High risk of bias	Participants or investigators enrolling participants could possibly foresee assignments and thus introduce selection bias, such as allocation based on: using an open random allocation schedule (e.g. a list of random numbers); using assignment envelopes without appropriate safeguards (e.g. if envelopes were unsealed or non­opaque or not sequentially numbered); alternation or rotation; date of birth; case record number; or any other explicitly unconcealed procedure.
	Unclear risk of bias	There is insufficient information to permit a judgement of low or high risk of bias.
Performance bias
Blinding of participants and personnel	Low risk of bias	Any one of the following: no blinding or incomplete blinding, but the review authors judge that the outcome is not likely to be influenced by lack of blinding; or blinding of participants and key study personnel ensured, and it is unlikely that the blinding could have been broken.
	High risk of bias	Any one of the following: no blinding or incomplete blinding, and the outcome is likely to be influenced by lack of blinding; or blinding of key study participants and personnel attempted, but it is likely that the blinding could have been broken, and the outcome is likely to be influenced by the lack of blinding.
	Unclear risk of bias	Any one of the following: insufficient information to permit a judgement of low or high risk of bias; or the study did not address this outcome.
Detection bias
Blinding of outcome assessment	Low risk of bias	Any one of the following: no blinding of outcome assessment, but the review authors judge that the outcome measurement is not likely to be influenced by lack of blinding; or blinding of outcome assessment ensured, and it is unlikely that the blinding could have been broken.
	High risk of bias	Any one of the following: no blinding of outcome assessment, and the outcome measurement is likely to be influenced by lack of blinding; or blinding of outcome assessment, but it is likely that the blinding could have been broken, and the outcome measurement is likely to be influenced by lack of blinding.
	Unclear risk of bias	Any one of the following: insufficient information to permit a judgement of low or high risk of bias; or the study did not address this outcome.
Reporting bias
Selective outcome reporting	Low risk of bias	The study protocol is available, and all of the study’s prespecified (primary and secondary) outcomes that are of interest in the review have been reported in the prespecified way.
	High risk of bias	Any one of the following: not all of the study’s prespecified primary outcomes have been reported; one or more primary outcomes is reported using measurements, analysis methods, or subsets of the data (e.g. subscales) that were not prespecified; one or more reported primary outcomes were not prespecified (unless clear justification for their reporting is provided, such as an unexpected adverse effect); one or more outcomes of interest in the review are reported incompletely so that they cannot be entered in a meta‐analysis; or the study report fails to include results for a key outcome that would be expected to have been reported for such a study.
	Unclear risk of bias	The study protocol is not available, and it is unclear whether the published reports include all expected outcomes.
Other bias
Bias due to problems not covered elsewhere in the table	Low risk of bias	The study appears to be free of other sources of bias.
	High risk of bias	There is at least one important risk of bias.
	Unclear risk of bias	There may be a risk of bias, but there is either: insufficient information to assess whether an important risk of bias exists; or insufficient rationale or evidence that an identified problem will introduce bias.