Table 2.

Review of the quality of studies determined using downs and black scoring system.

Sl. No.	Author	Reporting (Max: 11)	External validity (Max: 3)	Internal validity-bias (Max: 7)	Internal validity -confounding (selection bias) (Max: 6)	Total (27)
1.	Saultz et al. (2015), USA [40]	5	3	1	0	9
2.	Muus et al. (2011), Multinational [41]	11	3	4	2	20
3.	Licht et al. (2012), Multinational [41]	11	3	4	2	20
4.	Legendre et al. (2013), Multinational [27]	11	3	4	2	20
5.	Licht et al., (2015), Multinational [29]	11	3	4	2	20
6.	Greenbaum et al. (2014), Multinational [43]	11	3	3	1	18
7.	Greenbaum et al. (2016), Multinational [28]	11	3	3	1	18
8.	Greenbaum et al. (2012), Multinational [44]	10	3	3	0	16
9.	Loirat et al. (2011), Multinational [45]	10	3	3	0	16
10.	Fakhouri et al. (2016), Multinational [46]	11	3	4	2	20