Understanding Gene-Environment Interactions

Week 6 - Which models can explain the role of gene-environment interaction in mental health?

Gene-environment interactions (GxE) are situations where genetic influences on behaviour depend on the environment. The impact of a genotype on disorder risk is different in people with different environmental exposure. These types of interactions are hypothesised by the diathesis-stress framework, which implies that genetic vulnerability interacts with life stressors to trigger mental health disorders.

Figure 1: Two primary types of gene-environment interactions

Gene-environment interactions around depression are hypothesised to be fan-shaped (Figure 1a). In this type of interaction, the influence of genotype is greater in one environmental context than in another. In the presence of life stressors, genetically vulnerable individuals are more likely to develop depression, whereas in the absence of life stressors these individuals may be no more likely to develop depression. Another way to explain this is that only when adverse environmental conditions are experienced that the genes for disorder risk decide to "come online" (Dick, 2011).

Quantitative genetic studies point towards the likelihood of gene-environment interactions in risk environments for anxiety/depression (Nugent et al., 2011). A review of these studies points out that although quantitative genetic findings on GxE are quite limited, they are consistent (Rutter et al., 2006). Gene-environment interplay is an incredibly complex process. Understanding these complexities may help avoid misleading types of biological reductionism and stigma, whilst simultaneously drawing attention to the importance of genes in all risk and protection pathways.

References

Dick, D. M. (2011). Gene-environment interaction in psychological traits and disorders. Annual review of clinical psychology, 7(1), 383-409.

Nugent, N. R., Tyrka, A. R., Carpenter, L. L., & Price, L. H. (2011). Gene–environment interactions: early life stress and risk for depressive and anxiety disorders. Psychopharmacology, 214(1), 175-196.

Rutter, M., Moffitt, T. E., & Caspi, A. (2006). Gene–environment interplay and psychopathology: Multiple varieties but real effects. Journal of child Psychology and Psychiatry, 47(3‐4), 226-261.

Signing off,

burnt toast, sweet tea;

Image A: group of people gardening