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. Author manuscript; available in PMC: 2018 Jun 1.
Published in final edited form as: J Child Psychol Psychiatry. 2017 Feb 8;58(6):719–727. doi: 10.1111/jcpp.12691

Table 1.

Sample Demographics

N 2,399
Mean age in years (SD) 11.85 (2.87)
% female 51
% monozygous twins 40
% siblings of twins 9
% primary caregiver Caucasian 90
Median years of education (mother) 15
Median years of education (father) 14
Mean Full Scale IQ (SD) 105.97 (13.32)
% history of reading problems in school 37
% history of attention problems in school 21