Is relatively young age within a school year a risk factor for mental health problems and poor school performance? A population-based cross-sectional study of adolescents in Oslo, Norway

Table 2 Adjusted average scores and SD of total SDQ, five SDQ subscores, SCL-10 score, and grade in different relative age groups within a school year

	Oldest third		Middle third		Youngest third		p
	Mean	SD	Mean	SD	Mean	SD
Total SDQ score	9.81	4.85	9.74	4.88	9.78	4.85	0.81
SDQ Emotional	2.64	2.20	2.53	2.18	2.56	2.20	0.44
SDQ Hyperactivity	3.54	2.01	3.62	2.02	3.55	2.03	0.48
SDQ Conduct problems	2.12	1.61	2.15	1.59	2.15	1.63	0.84
SDQ Peer problems	1.49	1.47	1.49	1.51	1.58*	1.53	0.01
SDQ Pro social	7.45	1.80	7.37	1.82	7.35	1.84	0.97
SCL-10 score	0.79	0.51	0.78	0.51	0.76*	0.49	0.03
Average grade	4.01*	0.79	3.95	0.80	3.92	0.79	<0.001

Scores were adjusted for ethnicity, gender, parental education, and social support from family, class, teachers, and friends. * indicates the group that differed significantly from each other by Tukey's post hoc test (p = 0.05).

ISSN: 1471-2458