Several potential limitations of this study should be noted. First, although the total sample size far exceeds those from prior AD genetic studies, it is still relatively underpowered to detect common genetic variants of small effect expected for the genetic architecture of such complex phenotypes (37). Second, not all samples provided the same level of phenotypic coverage; in particular, some subjects in QIMR were missing diagnostic data for GAD or specific phobia. While this can produce bias, our forest plots, tests for heterogeneity, and internal validation analyses suggest that this likely did not bias our results. Third, consent agreements for some of the sites did not allow for sharing of subject data, so GWAS analyses had to be conducted separately using a standardized procedure and combined via meta-analysis. While this has been shown to approximate the power obtained when using raw data via mega-analysis (38), we were limited in our ability to conduct additional post-hoc analyses such as GPRS and GREML that require the use of raw GWAS data. Reassuringly, results obtained by applying LD score regression to summary statistics
