Table 2 Methodology and design of included studies

Quantitative

194

66%

 Cross-sectional study—representative sample

129

44%

 Cross-sectional study—convenience or purposive sample

42

14%

 Cohort study

23

8%

Qualitative

60

20%

 Interviews

21

7%

 Focus groups

21

7%

 Media analysis

8

3%

 Deliberative (e.g. citizen’s jury)

5

2%

 Document or submission analysis

3

< 1%

 Multiple qualitative methods

2

< 1%

Mixed methods

39

13%

 Media analysis

17

6%

 Multiple quantitative and qualitative methods

12

4%

 Cross-sectional survey—convenience sample

7

2%

 Document or submission analysis

1

< 1%

 Community-based participatory

1

< 1%

Total

293

100%