Characteristics of included studies
| Type of study design | N=418 | % |
| Case report | 220 | 52.6 |
| Case series | 30 | 7.2 |
| Cohort | 40 | 9.6 |
| Cross-sectional | 53 | 12.7 |
| Longitudinal | 9 | 2.2 |
| Randomised controlled trial | 10 | 2.4 |
| Retrospective medical record review | 54 | 12.9 |
| Review | 2 | 0.5 |
| Country of data collection | ||
| Australia | 15 | 3.6 |
| Canada | 8 | 1.9 |
| China | 12 | 2.9 |
| Denmark | 11 | 2.6 |
| France | 10 | 2.4 |
| Germany | 12 | 2.9 |
| India | 19 | 4.5 |
| Italy | 16 | 3.8 |
| Japan | 18 | 4.3 |
| Spain | 8 | 1.9 |
| Turkey | 22 | 5.3 |
| UK | 20 | 4.8 |
| USA | 143 | 34.2 |
| Other* | 104 | 24.9 |
| Decade of publication | ||
| 1980s | 2 | 0.5 |
| 1990s | 27 | 6.5 |
| 2000s | 76 | 18.2 |
| 2010s | 220 | 52.6 |
| 2020–2024 | 93 | 22.2 |
| Age groups† | ||
| Infancy (0–1 years) | 0 | 0.0 |
| Childhood (2–10 years of age) | 79 | 18.9 |
| Adolescence (11–17 years) | 179 | 42.8 |
| Mixed age groups (0–17 years) | 160 | 38.3 |
| Sex | ||
| Males (total N) | 2556 | 34.8 |
| Females (total N) | 4782 | 65.2 |
| Studies in which sex was not reported | 79 | – |
*Algeria (1), Austria (1), Bangladesh (1), Belgium (1), Bolivia (1), Bosnia (1), Brazil (1), Bulgaria (2), Croatia (2), Czech Republic (1), Egypt (1), Finland (4), Greece (5), Hong Kong (1), Hungary (2), Indonesia (1), Iran (2), Ireland (3), Israel (2), Kenya (1), Korea (6), Lebanon (1), Libya (1), Macedonia (1), Malaysia (4), Mexico (2), Nepal (1), Netherlands (6), New Zealand (1), Nigeria (2), Norway (4), Oman (1), Pakistan (3), Poland (4), Portugal (4), Qatar (2), Saudi Arabia (2), South Africa (2), Sri Lanka (1), Sweden (5), Switzerland (3), Taiwan (3), Thailand (5), Ukraine (2) and multiple countries in Africa (1).
†Based on the American Academy of Paediatrics; adolescence is divided into three groups according to this classification but was collapsed into one category for the purposes of this review (>10 years of age). Late adolescence, being 18–21 years of age, was excluded from this study.