Table 1. Demographic and clinical characteristics of the study groups.

	ASC (N=43)	Siblings (N=38)	Controls (N=40)	Group differences
Age (years)	14.52±1.74	14.99±2.13	15.06±1.63	Not significant
Gender (M/F)	28/15	12/26	20/20	No significant difference between controls and the other two groups Significant difference between ASC and siblings; P=0.002
Wechsler Abbreviated Scale of Intelligence	104.65±14.57	113.63±9.95	112.38±11.12	No significant difference between siblings and controls Significant differences between: ASC < Siblings; P=0.003 ASC < Controls; P=0.012
Social Communication Questionnaire	25.03±5.5	1.6±2.19	2.2±2.33	No significant difference between siblings and controls Significant differences between: ASC > Siblings; P<0.001 ASC > Controls; P<0.001
Autism Spectrum Quotient	38.59±6.72	8.61±5.63	9.1±5.59
Social Responsiveness Scale	112.85±31.13	17.22±12.34	15.43±11.4

Abbreviations: ASC, autism spectrum condition; F, female; M, male. Interval measurements are presented as a group mean with s.d. The significance of differences between the groups means in every measurement was calculated with t-tests for each pair of the groups.