Table 4.

Self-controlled case series analyses of subgroup

Risk period	MPH start within 3 years after ADHD diagnosis				MPH start within 1 years after ADHD diagnosis
	No. of events	IRR (95% CI)	pvalue		No. of events	IRR (95% CI)	pvalue
Total
Unexposed	1,701	1			1,474	1
Pre exposed: 90 d	104	11.7 (9.5−14.42)	< 0.001		87	12.41 (9.87−15.6)	< 0.001
Exposed	3,492	19.37 (17.77−21.11)	< 0.001		2,781	20.93 (19.02−23.03)	< 0.001
After exposed: 30 d	41	2.78 (2.04−3.81)	< 0.001		36	3.09 (2.21−4.32)	< 0.001
After exposed: 31−60 d	17	1.21 (0.75−1.95)	0.439		15	1.35 (0.81−2.25)	0.253
After exposed: 61−90 d	26	1.93 (1.3−2.84)	< 0.001		20	1.87 (1.2−2.92)	0.006
Age		1.58 (1.56−1.61)	< 0.001			1.62 (1.6−1.65)	< 0.001
Age 6 to 9 years
Unexposed	447	1			351	1
Pre exposed: 90 d	32	11.91 (8.19−17.31)	< 0.001		22	12.07 (7.7−18.91)	< 0.001
Exposed	1,777	17.21 (14.99−19.75)	< 0.001		1,328	18.5 (15.78−21.68)	< 0.001
After exposed: 30 d	11	1.72 (0.94−3.14)	0.079		9	1.81 (0.93−3.53)	0.082
After exposed: 31−60 d	4	0.69 (0.26−1.86)	0.464		3	0.67 (0.21−2.1)	0.493
After exposed: 61−90 d	9	1.7 (0.88−3.3)	0.117		8	1.96 (0.97−3.98)	0.061
Age		1.53 (1.5−1.56)	< 0.001			1.58 (1.54−1.62)	< 0.001

CI, confidence interval; MPH, methylphenidate; ADHD, Attention Deficit Hyperactivity Disorder.