Table 2. Mean SDQ subscale scores of 8,900 preschoolers from four cities in China, stratified by age and gender.

Age (years)/gender	n	Total difficulties	Emotional symptoms	Conduct problems	Hyperactivity/inattention	Peer problems	Pro-social behavior
3
Male	1,081	11.73 (4.57)	1.96 (1.63)	2.24 (1.42)	4.68 (2.19)	2.83 (1.55)	5.80 (2.09)
Female	1,006	11.26 (4.60)	2.12 (1.66)	2.11 (1.46)	4.45 (2.09)	2.56 (1.55)	6.40 (2.08)
4
Male	1,514	11.64 (4.68)	1.94 (1.62)	2.15 (1.45)	4.85 (2.23)*	2.68 (1.61)	6.08 (2.11)
Female	1,281	11.03 (4.67)	2.15 (1.77)*	1.97 (1.45)	4.48 (2.08)	2.42 (1.61)	6.68 (2.08)
5
Male	1,404	11.02 (4.79)	1.84 (1.69)	1.93 (1.49)	4.65 (2.28)*	2.58 (1.55)	6.48 (2.13)
Female	1,290	10.51 (4.84)	2.11 (1.84)*	1.80 (1.43)	4.19 (2.10)	2.39 (1.55)	6.96 (2.05)
6
Male	711	10.38 (4.55)*	1.71 (1.59)	1.83 (1.39)	4.46 (2.18)	2.37 (1.45)*	6.81 (2.08)
Female	613	10.30 (5.27)	2.10 (1.96)*	1.80 (1.55)	4.02 (2.25)	2.36 (1.60)	7.10 (2.10)
All
Male	4,710	11.29 (4.69)	1.88 (1.64)	2.06 (1.45)	4.69 (2.23)†	2.64 (1.56)	6.25 (2.13)
Female	4,190	10.82 (4.81)	2.12 (1.80)†	1.93 (1.47)	4.32 (2.12)	2.43 (1.58)	6.76 (2.09)

Scale completed by parents or guardians. Data presented as mean (standard deviation).

SDQ = Strengths and Difficulties Questionnaire.

^*p < 0.05;

^†p < 0.0001.