Sociodemographic description of the samples.

1p-values obtained from t test for age and socioeconomic status and from χ2 test for the number of males.2NS: non significant p-value.3We used the Blishen index [56] according to the highest socioeconomic status of the two parents. This index is based on education and income and on a Canadian census of 514 occupational categories according to the Canadian Classification and Dictionary of Occupations. Offspring and controls were not different on socioeconomic status. When the socioeconomic status was entered as a covariate, the difference between offspring and controls remained the same on the neuropsychological measures: Global IQ (pTOT (pDR (p IR (pDR (p