taken as causal as the sets of traits included in the model are unlikely to be longitudinal, much less measured in the same sample. However, it is specifically because the summary statistics can come from independent samples that presents such a unique opportunity in psychiatric comorbidity research. Namely, systems of relationships can now be examined in the same statistical model across rare, and even mutually exclusive traits, such as disorders that disallow one another (e.g., BIP and SCZ) and distinct developmental presentations within disorders (e.g., early and late onset versions of SCZ).
