| Number of studies | Participants | |
|---|---|---|
| Algeria | 1 | 253 |
| Argentina | 1 | 145 |
| Australia | 2 | 204 |
| Austria | 1 | 1005 |
| Bangladesh | 1 | 344 |
| Brazil | 3 | 2678 |
| Canada | 2 | 1129 |
| Colombia | 3 | 2456 |
| Croatia | 1 | 2860 |
| Egypt | 2 | 568 |
| Ethiopia | 2 | 950 |
| France | 2 | 1475 |
| Germany | 1 | 281 |
| Ghana | 1 | 760 |
| Greece | 1 | 200 |
| Hong Kong | 1 | 266 |
| Hungary | 1 | 262 |
| India | 2 | 1184 |
| Indonesia | 1 | 277 |
| Iran | 1 | 696 |
| Italy | 5 | 24,071 |
| Japan | 1 | 1468 |
| Jordan | 1 | 282 |
| Lebanon | 2 | 627 |
| Malaysia | 5 | 2210 |
| Mexico | 2 | 1395 |
| Morocco | 1 | 1435 |
| New Zealand | 1 | 43 |
| Nigeria | 2 | 707 |
| Pakistan | 3 | 940 |
| Palestine | 1 | 400 |
| Poland | 3 | 2812 |
| Portugal | 2 | 913 |
| Qatar | 2 | 227 |
| Romania | 1 | 546 |
| Russia | 1 | 307 |
| Saudi Arabia | 2 | 592 |
| Slovenia | 1 | 1271 |
| South Africa | 2 | 902 |
| Spain | 3 | 1196 |
| Sweden | 1 | 278 |
| Thailand | 1 | 405 |
| Tunesia | 1 | 603 |
| Turkey | 7 | 2427 |
| UK | 1 | 382 |
| United Arab Emirates | 1 | 543 |
| USA | 6 | 2918 |
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