We used the FACTOR procedure in SAS version 9.2 (SAS Institute Inc., Cary, NC) to determine the factor structure of ADsx, ASPDsx, ADHDsx, CDsx, DDsx, and NS scores. All phenotypes were entered into a principal component analysis using the default orthogonal rotation method. We then calculated factor scores for each individual with nonmissing data for all disinhibitory phenotypes and tested for association with these scores.
