The customization of diagnosis and treatment to individuals - is likely to have a role in clinical psychiatry. However, the extent to which this will be important and the proportions of individuals with a particular psychiatric disorder who might benefit from precision medicine is unclear and is now the subject of considerable research. Genomics is an important tool in the precision medicine toolbox. It is already important for several disorders and becoming common in clinical practice (e.g., in the evaluation of children with intellectual disability and pervasive developmental delay). However, these studies are mostly focused upon rare genetic variants of uncommonly large effect. For most individuals with serious psychiatric disorders whose risk is mediated by the cumulative effect of large numbers of common genetic variant with or without important environmental impacts, it is not yet clear whether genomics will be an important part of precision medicine in psychiatry. We know that these genetic effects significantly impact risk10,29 but the effects are not deterministic.
