Genomics of human complex trait variation may be a first step in understanding the genetics underlying human trait variation. In the future, we wish to explore other types of variation, for example, due to rare variants or to other types of structural variants, affecting brain function. Genetic studies addressing these traits are increasingly considering other ‐omics levels to address variation and the pathways between genotype and phenotype. Methylation studies for cognition and educational attainment (Dongen et al., 2018; Linnér et al., 2017) have uncovered multiple genome‐wide significant differences in methylation at CpG sites. Genome‐wide testing of epigenetic marks has been explored within ENIGMA for subcortical volumes; differentially methylated regions in the genome were suggested to be associated with hippocampal volume (Jia et al., 2019). DNA methylation at these loci affected expression of proximal genes among other traits in learning and memory (Jia et al., 2019). Other ‐omics that are promising include transcriptomics and metabolomics (van der Lee et al., 2018), possibly combined into multi‐omics approaches (Wu et al., 2018). We feel that these techniques are especially suitable for the investigation of changes in brain maturation, behavioral, development, and decline or resilience to decline in older age.
