Table 1.

Means, standard deviations and ranges for the Conners’ ADHD subscales by sex and zygosity

	Twin 1 Mean (SD)	Twin 2 Mean (SD)	Range
Parent
MZ
Hyperactivity–impulsivity
Male	7.45 (5.92)	7.10 (5.42)	0–23
Female	5.28 (4.38)	4.60 (3.93)	0–20
Inattention
Male	6.80 (5.78)	6.93 (5.22)	0–26
Female	4.71 (4.50)	4.68 (4.09)	0–21
DZSS
Hyperactivity–impulsivity
Male	7.50 (5.85)	6.66 (5.61)	0–27
Female	4.76 (4.27)	6.01 (5.44)	0–23
Inattention
Male	6.58 (5.51)	7.17 (6.45)	0–27
Female	5.84 (5.09)	5.55 (5.72)	0–26
DZOS
Hyperactivity–impulsivity
Male	6.93 (5.18)		0–24
Female		4.99 (4.78)	0–25
Inattention
Male	7.56 (6.01)		0–27
Female		4.99 (4.66)	0–23
Teacher
MZ
Hyperactivity–impulsivity
Male	3.65 (4.70)	3.59 (4.89)	0–25
Female	2.15 (3.43)	1.75 (2.31)	0–16
Inattention
Male	5.72 (5.15)	5.79 (5.41)	0–24
Female	3.31 (3.79)	3.32 (3.62)	0–21
DZSS
Hyperactivity–impulsivity
Male	5.54 (6.24)	3.90 (5.09)	0–25
Female	2.21 (3.70)	1.49 (3.07)	0–25
Inattention
Male	6.65 (6.21)	6.18 (5.95)	0–27
Female	3.58 (4.03)	3.72 (4.14)	0–24
DZOS
Hyperactivity–impulsivity
Male	4.40 (5.70)		0–27
Female		2.64 (3.82)	0–19
Inattention
Male	6.96 (7.10)		0–27
Female		3.95 (5.05)	0–25

Means and standard deviations prior to transformation

MZ monozygotic, DZSS dizygotic same-sex twin pairs, DZOS dizygotic opposite-sex twin pairs