TABLE 2.

Cox regression results of offspring ADHD diagnosis by acetaminophen exposure during pregnancy

	Time at risk in years	Number of children	Model 1 Unadjusted	Model 2 Adjusted a	Model 3 Adjusted and controlled for family effect b	Family effect from Model 3
	(Incidence rate per 100 person years)		HR 95% C.I.	aHR 95% C.I.	aHR 95% C.I.	aHR 95% C.I.
No acetaminophen use	104,804 (0.31)	12,080	Reference	Reference	Reference	Reference
Acetaminophen 1–7 days	55,726 (0.32)	6,490	1.07	0.87	0.75	0.94
			0.90–1.31	0.70–1.08	0.56–1.03	0.72–1.25
Acetaminophen 8–28 days	20,229 (0.43)	2,409	1.44	1.13	0.93	1.17
			1.14–1.86	0.82–1.49	0.59–1.46	0.79–1.68
Acetaminophen 29 days or more	3,855 (0.73)	469	2.47	2.02	1.06	2.77
			1.60–3.67	1.17–3.25	0.51–2.05	1.48–5.05

Abbreviations: HR, Hazard Ratio; C.I., bias corrected bootstrap 95% confidence interval (1,000 replications).

The rightmost column shows the family effect in the sibling control model.

^a Adjusted for propensity scores and maternal education and parity.

^b Adjusted for propensity scores.