Table 2.

Night-time sleep duration for ADHD cases and rest of cohort

	ADHD cases			Rest of cohort
Time point	N	Mean	SD	N	Mean	SD	P-value*
6 months	164	10 h 35 min	1 h 24 min	7573	10 h 48 min	1 h 19 min	0.04
18 months (1 year 6 months)	156	11 h 16 min	1 h 09 min	7431	11 h 19 min	1 h 02 min	0.50
30 months (2 years 6 months)	143	11 h 08 min	1 h 04 min	6986	11 h 14 min	0 h 58 min	0.20
42 months (3 years 6 months)	147	11 h 13 min	1 h 0 min	7143	11 h 16 min	0 h 52 min	0.47
69 months (5 years 9 months)	146	11 h 0 min	0 h 56 min	7056	11 h 17 min	0 h 41 min	<0.001
81 months (6 years 9 months)	143	10 h 50 min	0 h 51 min	7048	11 h 08 min	0 h 40 min	<0.001
115 months (9 years 7 months)	137	10 h 13 min	0 h 48 min	6741	10 h 27 min	0 h 39 min	<0.001
140 months (11 years 8 months)	126	9 h 44 min	0 h 50 min	6164	9 h 49 min	0 h 38 min	0.19

ADHD, attention deficit hyperactivity disorder.

^*t-test.