Table 1.
Demographic and Cognitive Characteristics of Sample
| Schizophrenia |
Siblings |
Controls |
Effect sizes |
|||||||||
| N | 496 | 505 | 823 | |||||||||
| Age* | 35.5 (10.1) | 36.7 (10.1) | 32.6 (9.7) | |||||||||
| Female*, n (%) | 127 (25.6) | 301 (59.6) | 458 (55.6) | |||||||||
| Education* | 14.0 (2.2) | 15.9 (2.4) | 16.7 (2.5) | |||||||||
| C/AA/O, n* | 412/27/57 | 445/12/48 | 669/76/73 | |||||||||
| Cognitive Variable** | Mean | SD | Msg | Mean | SD | Msg | Mean | SD | Msg | ES SZ<HC | ES Sib<HC | |
| WAIS Digit Symbol**** | 8.0 | 2.3 | 26 | 11.6 | 2.5 | 11 | 12.5 | 2.5 | 25 | −1.85 | −0.36 | |
| Trails A T-score**** | 37.3 | 10.5 | 28 | 46.0 | 10.4 | 16 | 48.0 | 10.2 | 24 | −1.04 | −0.19 | |
| Trails B T-score**** | 39.6 | 11.0 | 35 | 49.6 | 9.9 | 15 | 52.2 | 10.2 | 24 | −1.20 | −0.26 | |
| WMS Digit Span Forward*** | 8.5 | 2.0 | 32 | 9.6 | 1.9 | 18 | 9.8 | 1.8 | 172 | −0.69 | −0.11 | |
| WMS Digit Span Backward*** | 6.4 | 2.3 | 32 | 7.8 | 2.2 | 17 | 8.1 | 2.2 | 175 | −0.76 | −0.14 | |
| WAIS Letter Number Sequence | 9.4 | 2.7 | 225 | 11.9 | 2.8 | 249 | 12.3 | 2.4 | 132 | −1.16 | −0.16 | |
| WMS Logical Memory 1**** | 17.5 | 7.9 | 28 | 26.7 | 7.1 | 13 | 27.9 | 6.8 | 24 | −1.44 | −0.17 | |
| WMS Logical Memory 2**** | 12.6 | 7.9 | 32 | 22.3 | 8.0 | 15 | 24.0 | 7.5 | 28 | −1.49 | −0.22 | |
| WMS Verbal Paired Association*** | 16.2 | 4.7 | 51 | 19.8 | 3.3 | 46 | 20.2 | 2.9 | 346 | −1.03 | −0.13 | |
| CVLT Trials 1–5 Total*** | 41.4 | 12.7 | 102 | 58.7 | 9.5 | 69 | 59.2 | 8.9 | 156 | −1.70 | −0.05 | |
| WMS Visual Reproduction 1*** | 30.5 | 7.0 | 34 | 35.3 | 3.9 | 19 | 35.5 | 3.3 | 344 | −0.92 | −0.06 | |
| WMS Visual Reproduction 2*** | 25.2 | 9.3 | 37 | 33.1 | 5.1 | 19 | 33.7 | 4.4 | 347 | −1.17 | −0.13 | |
| WCST % Perseverative Errors T-score**** | 39.8 | 11.7 | 57 | 46.8 | 8.9 | 28 | 49.2 | 9.1 | 76 | −0.93 | −0.27 | |
| WCST Categories Over Trials**** | 0.04 | 0.02 | 49 | 0.06 | 0.02 | 23 | 0.07 | 0.02 | 52 | −1.50 | −0.50 | |
| WCST Correct Over Trials**** | 0.64 | 0.17 | 50 | 0.79 | 0.11 | 23 | 0.80 | 0.11 | 52 | −1.18 | −0.09 | |
| Nback One**** | 0.65 | 0.26 | 186 | 0.83 | 0.18 | 154 | 0.88 | 0.13 | 107 | −1.28 | −0.34 | |
| Nback Two**** | 0.49 | 0.22 | 190 | 0.69 | 0.20 | 151 | 0.76 | 0.18 | 99 | −1.40 | −0.38 | |
| Nback Three**** | 0.43 | 0.17 | 189 | 0.55 | 0.18 | 151 | 0.64 | 0.18 | 100 | −1.19 | −0.50 | |
| WAIS Arithmetic**** | 8.6 | 2.5 | 25 | 10.8 | 2.5 | 11 | 11.1 | 2.5 | 24 | −1.00 | −0.12 | |
| WAIS Similarities | 9.7 | 2.5 | 25 | 11.1 | 2.5 | 11 | 10.9 | 2.1 | 25 | −0.53 | 0.09 | |
| WAIS Picture Completion | 8.9 | 2.6 | 25 | 10.5 | 2.5 | 11 | 10.3 | 2.5 | 25 | −0.55 | 0.08 | |
| WRAT Reading Standard Score**** | 102 | 11.2 | 25 | 107 | 9.9 | 11 | 108 | 8.9 | 27 | −0.61 | −0.11 | |
| Benton Line | 24.5 | 5.1 | 35 | 27.4 | 3.5 | 20 | 27.5 | 3.5 | 31 | −0.72 | −0.03 | |
| Letter Fluency**** | 34.4 | 11.2 | 29 | 42.3 | 11.2 | 15 | 44.8 | 10.8 | 24 | −0.95 | −0.23 | |
| Category Fluency**** | 37.7 | 11.1 | 30 | 51.1 | 10.3 | 15 | 52.7 | 10.5 | 24 | −1.40 | −0.15 | |
| Mean ES | −1.07 | −0.17 | ||||||||||
Note: C/AA/O, Caucasian/African American/Other; SD, standard deviation, Msg, number missing; ES SZ<HC, effect size (Hedges’ g) for the schizophrenia impairment relative to controls; ES Sib<HC, effect size (Hedges’ g) for the sibling impairment relative to controls; WAIS, Wechsler Adult Intelligence Scale; WMS, Wechsler Memory Scale; CVLT, California Verbal Learning Test; WCST, Wisconsin Card Sorting Test; WRAT, Wide Range Achievement Test. “WCST Categories Over Trials” and ‘WCST Correct Over Trials”—to equate different versions of the WCST used at different times, categories and correct variables were divided by the number of trials administered. “Nback One,” “Nback Two,” and “Nback Three” scores are proportions correct.
Subgroup demographic differences significant at P < .001.
Controlling for age, gender, and race/ethnicity, schizophrenia < sibling and control at P < .001 for all cognitive measures.
Controlling for age, gender, and race/ethnicity, sibling < control at P < .05.
Controlling for age, gender, and race/ethnicity, sibling < control at P < .01.