second assessment. Fourth, this series of models, to the best of our knowledge, provides the first estimates of “true” individual-specific etiology of LTH-AD in men. Moreover, we found that 51% of what would in a standard twin model be attributed to individual-specific environment was in fact error of measurement, whereas 49% was true individual-specific environment. Finally, when accounting for unreliability in the twin model, LTH-AD in men was found to have a heritability point estimate of 71%. This revised estimate for the heritability of AD puts it in the range of the heritability reported for more severe psychopathology such as bipolar disorders (Smoller and Finn, 2003) and schizophrenia (Sullivan et al., 2003).
