Approximately 4% of females and 18% of males met lifetime criteria for CD, and approximately 4% of females and 16% of males met lifetime criteria for AAB. These prevalences of CD and AAB are consistent with prevalence estimates reported in previous studies.5 Means and standard deviations for the symptom counts of CD and AAB are presented in Table 1. Measures of CD and AAB demonstrated significant positive skew, and a log transformation was performed prior to the genetic analyses in order to improve the normality of these measures. The skew of the CD symptom count was 2.52 and 1.16 before and after the log transformation, and the skew of the AAB symptom count was 1.89 and 0.99 before and after the log transformation.
