Table 3. Risk of bias of included studies evaluated by Newcastle–Ottawa scale (NOS).

For each type of bias mentioned, an asterisk (*) indicates the chance of bias, with subsequently higher chances of bias with each added asterisk (*)

Study	Newcastle–Ottawa Scale			Overall risk of bias
	Selection (max 4*)	Outcome/exposure (max 3*)	Comparability (max 2*)
Jacobs et al., USA, Dec 2020 [7]	**	**	**	Moderate
Fisher et al., USA, Jan 2021 [8]	***	**	**	Moderate
Walsh-Messinger et al., USA, Nov 2020 [9]	**	**	*	High
Halpin et al., UK, Feb 2021 [10]	***	**	*	Moderate
Islam et al.; Bangladesh, Feb 2021 [11]	***	**	*	Moderate
Huang et al.; USA, Mar 2021 [12]	**	**	*	Moderate
Carfi et al., Italy, Jul 2020 [13]	***	**	*	Moderate