Systematic Review: Molecular Studies of Common Genetic Variation in Child and Adolescent Psychiatric Disorders.

ABSTRACT Objective We conducted a systematic review of studies using molecular genetics and statistical approaches to investigate the role of common genetic variation in the development, persistence, and comorbidity of childhood psychiatric traits. Method A literature review was performed on the Pubmed database, following the Preferred Reporting Items for Meta-Analyses (PRISMA) guidelines. There were 131 studies meeting inclusion criteria, having investigated at least one type of childhood-onset or childhood measured psychiatric disorder or trait with the aim of 1) identifying trait-associated common genetic variants, 2) estimating the contribution of single nucleotide polymorphisms (SNPs) to the amount of variance explained (SNP-heritability), 3) investigating genetic overlap between psychiatric traits, or 4) investigating whether stability in traits or the association with adult traits is explained by genetic factors. Results The first robustly associated genetic variants have started to be identified for childhood psychiatric traits. There were substantial contributions of common genetic variants to many traits, with variation in SNP-heritability estimates depending on age and raters. Moreover, genetic variants also appeared to explain comorbidity as well as stability across a range of psychiatric traits in childhood and across the lifespan. Conclusion Common genetic variation plays a substantial role in childhood psychiatric traits. Increased sample sizes will lead to increased power to identify genetic variants and to understand genetic architecture, which will ultimately be beneficial to targeted and prevention strategies. This can be achieved by harmonizing phenotype measurements as is already proposed by large international consortia and by including the collection of genetic material in every study.