Table 2

Summary of the included studies by country

Country	Sex	Ages (years)	Sample size	Country–sex–age–year groups	Span of years
Australia^w1–w12	Boys+girls	9–16	25 961	101	1988–2010
Belgium^w13–w23	Boys+girls	9–17	23 358	117	1985–2010
Brazil^w24–w26	Girls	9–17	2826	24	1998–2006
Canada^w27–w32	Boys+girls	9–17	29 009	91	1981–2011
Estonia^{w21,w33–w38}	Boys+girls	10–17	7906	46	1992–2002
France^{w18,w39–w45}	Boys+girls	9–14	5763	32	1985–2007
Greece^{w18,w46–w50}	Boys+girls	9–17	268 382	55	1991–2014
Hungary^{w18,w21,w51,w52}	Boys+girls	12–17	2455	22	1990–2013
Italy^{w18,w53–w58}	Boys+girls	12–17	5218	31	1986–2007
Japan^w59–w75	Boys+girls	9–17	279 732	306	1998–2014
Lithuania^w34,w35	Boys+girls	11–17	6479	28	1992–2002
The Netherlands^w76–w78	Boys+girls	12–16	3457	22	1987–2006
Poland^w79–w82	Boys+girls	13–17	22 895	19	1992–2007
Portugal^w83–w89	Boys+girls	9–17	29 857	71	1999–2011
Seychelles^w90,w91	Boys+girls	11–16	7913	24	1990–2004
South Africa^w92–w99	Boys+girls	11–16	2668	30	1996–2012
Spain^{w18,w100–w112}	Boys+girls	9–17	25 950	151	1985–2010
UK^w113–w126	Boys+girls	9–16	48 535	116	1986–2014
USA^w127–w137	Boys+girls	9–17	166 900	122	1995–2013