This study has limitations. First, some study samples had small coverage over some birth cohorts (e.g., AAND had no one born <1945). Due to differences in recruitment criteria, we controlled for study sample in all models, but the overlap in sample and coverage may have led to over controlling for invariance with the addition of study sample in the model. However, no single study sample provided all data for a birth cohort, and sensitivity analyses indicated similar results when controlling versus not controlling for the study sample. A related concern involved the different eligibility criteria for the included studies, but controlling for sample should have helped to control this variability. Notably, the overall model fit indices revealed poor fit in baseline and final MIMIC models. While this suggests substantial variation in the ability of the model to reproduce the overall data, there was no notable difference in fit between models that did and did not adjust for measurement non-invariance. This suggests that model fit was driven by variation in the data (e.g., current FTND had poorer model fit than lifetime
