Editorial: Genome-wide Association Studies of Internalizing Symptoms: A Big Step on a Long Road

Anxiety and depression are collectively the most common mental illnesses, affecting 15% of the world's population in any given year.¹ Together, they account for the greatest global burden of ongoing disability of any disorder, mental or physical.² They frequently emerge early in life as internalizing disorders in childhood or adolescence, and have long-lasting effects on mental wellbeing, acting as risk factors for mental illnesses in adulthood.³ As such, understanding the causes of these disorders is imperative. Internalizing disorders are influenced by multiple environmental and genetic factors, and research from twin studies has indicated that they have a genetic contribution (heritability) of 40% to 50%.⁴ However, implicating specific genetic variants through genome-wide association studies (GWAS) has been challenging, in part due to the need to obtain large sample sizes and the logistical difficulty of doing so. In this issue of the Journal, Jami et al. present an innovative meta-analysis that is a major step toward an understanding of specific variants.⁵.