First, a general transmission only model was fit to the five family types. To simplify the model, the general transmission effects across siblings were constrained to be the same for the families with (1) DZ twins and non-twin biological offspring, and (2) families with two adoptive children and families with both an adoptive and biological child. This general transmission model provided a good fit to the data, with values for the fit indices listed in Table 1. This model served as the baseline model for all subsequent models that incorporated disorder specific transmission effects.
