The data were analyzed using an additive genetic model in a family-based association test performed in FBAT (Rabinowitz and Laird 2000). FBAT builds on the original Transmission Disequilibrium Test (TDT) (Spielman et al. 1993), where alleles transmitted to extreme offspring are compared to the expected distribution of alleles among offspring under Mendel's law of segregation and conditioning. Three phenotypes were analyzed using an additive test in FBAT: adolescent/young adult CD, adolescent/young adult AAD, and adult AAD.
