Table 1.

Demographic characteristics (mean ± standard deviation) and total GM volume by sex and group

	Parents	Controls	t Statistic (df=22)
Demographic characteristics
Age (years)	39.59 ± 5.99	38.31 ± 6.37	0.71, NS
Education	15.83 ± 1.70	16.61 ± 1.95	1.25, NS
Handednessa	0.80 ± 0.35	0.78 ± 0.31	0.17, NS
SESb	49.15 ± 8.06	49.57 ± 6.81	0.19, NS
Full scale IQ	115.83 ± 7.70	119.17 ± 9.61	1.35, NS
Verbal IQ	114.78 ± 8.61	114.09 ± 9.85	0.25, NS
Performance IQ	113.48 ± 11.52	119.87 ± 9.70	2.22, P<0.05
Total GM (ml)c
	Parents	Controls
	Male: 767	Male: 754	0.31, NS
	Female: 658	Female: 666	0.36, NS

NS, non significant; GM, gray matter.

^aHandedness was assessed using the Annett Handedness Questionnaire [II]. Scale ranges from −1.0 (left-handed) to 1.0 (right-handed). The score was obtained by dividing total of right preference (+ 1), either hand (0), and left preference (− 1) items by 12.

^bSocioeconomic status (SES) was determined by Hollingshead 4-Factor Index of Social Status [12].

^cNo group differences were observed in total GM although GM differed by sex (males > females) whether collapsed across group (P<0.0001) or separated by group (parent males > parent females, P = 0.002; control males > control females, P = 0.007).