Interactions gène-environnement dans les troubles psychiatriques

Both genetic and environmental factors play important roles in the development of severe mental disorders such as schizophrenia, bipolar disorder, and depression. While environmental risk factors contribute heavily to severe mental disorders, there is also significant evidence of marked individual differences in susceptibility to adverse environmental exposures. The combination of very high heritability and strong environmental factors suggests that severe mental disorders are the result of the interaction between genetic and environmental factors rather than independent main effects. Gene–environment interactions represent a causal mechanism where the genetic factors influence sensitivity to environmental exposures. Over the last twenty years, advances in genetics technology have enabled the study of the interplay between genes and the environment at the level of an individual's measured DNA. The first gene–environment interaction studies were restricted to the exploration of one or more polymorphisms in one or more genes (the so-called gene candidate approach). These genes were selected based on their presumed function in relation to the disorder or the environmental factor of interest. To overcome the limitations of the gene candidate approach, psychiatric research has recently begun to develop genome-wide environment interaction studies to search the entire genome for genetic variants that moderate the effects of the environment on severe mental disorders. While the diathesis-stress model has been the guiding conceptual model for the majority of gene–environment interaction studies, it has recently been thrown into question by the differential susceptibility theory, which suggests that certain individuals are genetically more sensitive to environmental exposures. On the one hand, such individuals may be more prone to developing a psychopathology in response to adverse environments, on the other hand, higher genetic susceptibility may also make them more likely to benefit from favorable environmental situations.