Table 2.

Critical appraisal of the longitudinal cohort and case-control studies included for analysis

References	Analytical breadtha	Analytical deptha	Selectionb	Comparabilityb	Outcome/Exposureb	Totalc
Cohorts
Barnett and Brennan (1998)[40]	**	***	**	**	**	5;6
Bromet et al. (1988)[39]	**	**	**	**	***	4;7
Fuhrer et al. (1999)[131]	***	***	*	**	*	6;4
Griffin et al. (2002)[37]	**	**	**	**	*	4;5
Marchand et al. (2005)[12]	***	***	***	**	**	6;7
Niedhammer et al. (1998)[38]	**	**	*	**	*	4;4
Revicki et al. (1993)[129]	*	*	*	**	*	2;4
Shields (1999)[132]	**	**	***	**	**	4;7
Shields (2002) [130]	**	***	**	**	**	5;6
Smith et al. (2008)[133]	***	**	**	**	**	5;6
Stansfeld et al. (1998)[134]	***	***	*	**	**	6;5
Wickrama et al. (2007)[36]	**	*	*	*	**	3;4
Case-control
Ostry et al. (2006)[35]	*	*	**	**	**	2;6

Note. Full details on the scoring system are presented in Additional file 2.

^a Criterion considered for the conceptual assessment of the study quality.

^b Criterion considered for the methodological assessment of the study quality.

^c Total scores were obtained by summing the number of stars allocated to the conceptual and methodological components of the critical appraisal respectively.