Full scale IQ scores were derived from the Wechsler Adult Intelligence Scale – Revised Edition (WAIS-R). Based on a priori theoretical considerations (Green et al., 2004; Hill, Schuepbach, Herbener, Keshavan, & Sweeney, 2004; Kareken et al., 1995; Milev, Ho, Arndt, & Andreasen, 2005; Saykin et al., 1994), 40 test variables from the standardized neuropsychological battery were grouped into 6 cognitive domains: Verbal Memory, Processing Speed/Attention, Problem Solving, Language, Visuospatial Abilities and Motor Skills. These cognitive domain groupings had good internal consistency (Median Cronbach’s alpha=0.80; Range=0.75–0.85)(Ho et al., 2003; Milev et al., 2005). The component neuropsychological test variables used to compute each cognitive domain score have been previously described (Milev et al., 2005). For Processing Speed/Attention domain score, these were: WAIS-R Digit Span, WAIS-R Digit Symbol, Trail Making A, and Stroop Color and Word Test (trials 1–3). Problem Solving domain score comprised of Wisconsin Card Sorting Test (WCST) number of categories attained, WCST number of perseverative errors, Shipley Institute of Living Scale abstractions subtest, WAIS-R Comprehension, Similarities, Picture Completion and Picture Arrangement subtests. Prior to deriving cognitive domain scores, raw test
