. Author manuscript; available in PMC: 2011 Sep 1.

Published in final edited form as: J Dev Behav Pediatr. 2010 Sep;31(7):533–544. doi: 10.1097/DBP.0b013e3181ef42a1

Table 2.

Etiology of group deficits in reading, math, and ADHD symptoms

	MZ pairs^a				DZ pairs^a
		Proband	Co-twin		Proband	Co-twin
	N^b	M (SD)	M (SD)	N^b	M (SD)	M (SD)	h²_g (SE)
Reading	106	−2.00 (0.68)	−1.73 (0.75)	89	−1.99 (0.72)	−1.07 (1.23)	0.65 (0.13)^***
Math	91	−2.01 (0.56)	−1.38 (0.99)	84	−2.04 (0.55)	−0.81 (1.12)	0.58 (0.15)^***
Inattention	98	−2.03 (0.58)	−1.46 (1.23)	83	−2.07 (0.59)	−0.59 (1.07)	0.87 (0.14)^***
Hyperactivity - impulsivity	85	−2.17 (0.57)	−1.47 (0.58)	65	−2.09 (0.58)	−0.62 (1.16)	0.76 (0.15)^***

Note.

^***

P < .001.

Scores are expressed as standard deviations from the estimated population mean. All scores are scaled so that lower scores indicate greater impairment on all measures.

Total number of pairs in which at least one twin met the criteria for the proband group (score at least 1.25 SD below the population mean).