to the sum score of the items is likely, in part, a reflection of the fact that the sum score in UKB was created using listwise deletion, resulting in a reduced sample size of 274,008. Conversely, Genomic SEM uses all available information from neuroticism items, with sample sizes of ~325,000 each. In more severe cases of sample non-overlap, we would expect even larger power benefits of Genomic SEM-derived summary statistics relative to individual items or sum scores. Indeed, in instances of minimal sample overlap, it is not possible to compute sum scores, but Genomic SEM can still be used to integrate data across phenotypes.
