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Summary of the main features of retrieved studies
| Studies research design | |
| Case–control | 2 |
| Cohort | 30 |
| Cross-sectional | 41 |
| Ecological | 28 |
| Samples | |
| Cross-national population samples | 16 |
| National population samples | 66 |
| Regional/community samples | 19 |
| Geographical allocation of studies’ samples | |
| EU | 61 |
| North America (USA and Canada) | 18 |
| Australasia (Australia and New Zealand) | 7 |
| Asia (China, Japan, South Korea) | 6 |
| South America (Argentina and Brazil) | 2 |
| Multicentre | 7 |
