Gene–environment interaction

Gene–environment interaction occurs when the effect of genetic differences on a trait depends on environmental conditions, or the effect of an environment depends on genotype.

Reaction norm: A function or curve showing how a genotype’s phenotype changes across environmental conditions. Reaction norms depict the genotype-specific responses that define interaction.
Caspi et al. 2002 MAOA study: A study reporting that childhood maltreatment predicted antisocial outcomes more strongly among males with low-activity MAOA variants. It became a prominent candidate example of genotype-dependent response to maltreatment.
Gene–environment correlation: The tendency for genetic differences to be associated with differences in environmental exposure. It concerns exposure patterns, whereas interaction concerns variation in responses to exposure.
Pharmacogenomics: The study of how genetic variation influences responses to medicines. Drug effects can differ by genotype, making treatment a measurable environmental exposure.
Candidate gene study: A genetic association study testing variants selected because of a hypothesized biological role. Many early interaction claims came from candidate-gene designs with limited statistical power.
Differential susceptibility: A model in which some individuals are more affected than others by both adverse and supportive environments. It captures genetic variation in sensitivity across environmental extremes.
5-HTTLPR and stress: Research examining whether variation in the serotonin transporter promoter modifies associations between stressful life events and depression. This proposed interaction became a major test case in psychiatric genetics.
Mediation (statistics): A statistical framework describing an intermediate variable through which an exposure affects an outcome. Mediation asks how an effect travels; interaction asks whether effects differ across conditions.
Precision medicine: An approach to healthcare that uses individual characteristics to guide prevention and treatment. Gene–environment evidence can help explain why one intervention benefits some people more than others.
Genome-wide association study: A study testing genetic variants across the genome for statistical association with a trait. Genome-wide designs offer broader discovery but require enormous samples for interaction tests.

Linked from 40 pages