Misclassification among disorders could inflate estimates of genetic correlation and/or coheritability46. Indeed, some level of misclas-sification in psychiatric disorders is expected. For example, longitudinal studies47,48 of first admissions with psychosis showed that, with long-term follow-up, ~15% of subjects initially diagnosed with bipolar disorder were rediagnosed with schizophrenia, whereas ~4% of schizophrenia diagnoses were reclassified as bipolar disorder. Cases selected for GWAS contributing to PGC are more likely to have achieved a stable diagnosis compared to first-admission cases. However, assuming these levels of misclassification, the genetic correlation between bipolar disorder and schizophrenia for true diagnoses is still high, estimated46 to be 0.55. Likewise, because a modest proportion of cases diagnosed with major depressive disorder, when followed over time, ultimately meet criteria for bipolar disorder49, our estimated genetic correlation between these two disorders may be modestly inflated by misclassification. However, if moderate-to-high genetic correlations between the major adult disorders are true, then overlapping symptoms and misdiagnosis among these disorders might be expected. The rg SNP value between schizophrenia and major depressive disorder is also unlikely to reflect misdiagnosis because misclassification between these
