Twenty-six carriers of the CTCTAC haplotype were identified in the group of 181 patients. Four homozygotes were identified, but they were grouped with the heterozygotes because they did not significantly differ from heterozygotes. Thus, all analyses were conducted between two groups: carriers and noncarriers. There were no significant differences between carriers and noncarriers, respectively, in sex (23.08% versus 32.90% were women) (χ2=1.73, df=1, p<0.19), age (mean=40.65 years, SD=9.68, versus mean=38.74, SD=10.59) (t=0.36, df=179, p=0.72), age at onset of schizophrenia (mean=20.72, SD=5.13, versus mean=21.12, SD=6.04) (t=–0.34, df=172, p=0.73), duration of illness (mean=19.60 years, SD=11.02, versus mean=17.35 years, SD=10.47) (t=0.76, df=170, p=0.45), or Global Assessment of Functioning Scale (GAF) score (mean=37.46, SD=10.29, versus mean=37.97, SD=15.77) (t=–0.27, df=172, p<0.79). A multiple linear regression assessing the ability of these variables to predict the overall negative symptom rating was not significant (F=0.72, df=5, 99, p<0.61). Therefore, these variables were excluded from further analyses.
The MANOVA revealed significant group differences (F=3.84, df=3, 177, p=0.01), and post hoc t tests revealed that carriers had significantly higher ratings than noncarriers on all three items (F1): avolition (t=2.08, df=180, p<0.04), alogia (t=2.60, df=180, p<0.02), and flattened affect (t=2.45, df=180, p<0.02). Ratings for all three items were combined to produce an overall negative symptom rating. A univariate ANOVA comparing the mean overall negative symptom rating of carriers (mean=5.85, SD=2.09) with that of noncarriers (mean=4.57, SD=1.77) indicated that CTCTAC carriers had higher overall ratings (F=10.93, df=1, 180, p=0.001). This difference remained significant after covarying for the global neurocognitive measure and the WRAT-3 (F=5.02, df=1, 131, p<0.03).