The final dataset consisted of 33 332 cases and 27 888 controls (including pseudocontrols formed from non-transmitted alleles) distributed among the five disorder groups: autism spectrum disorders (4788 trio cases, 4788 trio pseudocontrols, 161 cases, 526 controls), attention deficit-hyperactivity disorder (1947 trio cases, 1947 trio pseudocontrols, 840 cases, 688 controls), bipolar disorder (6990 cases, 4820 controls), major depressive disorder (9227 cases, 7383 controls), and schizophrenia (9379 cases, 7736 controls). The results of the primary fixed-effects meta-analysis for all five disorders, incorporating seven multidimensional scaling components as covariates, yielded a genomic control value of λ=1·167. The λ1000 (λ rescaled to a sample of 1000 cases and 1000 controls) was 1·005 (appendix p 22). In view of evidence for substantial polygenic contributions to common psychiatric disorders, this estimate probably shows the aggregate small effect of a large number of risk variants, although a moderate degree of population stratification or technical bias cannot be excluded.
