Twin Methodology

Our mental and psychological health and behavior are shaped by a combination of genetics and environment—our experiences, lifestyles, and living conditions. It is these environmental factors and their influence on human health and behavior that we at the Center for Environmental Neuroscience investigate. Compared to the rest of the population, twins have greater genetic similarity and often share similar environmental factors such as household and living environment during their upbringing. Twins are therefore uniquely placed to provide insights into the relationship between genetics, health, and the environment.

Our aim is to study the effects of the physical environment on the individual. We believe that the complexity of environmental factors has a critical influence on the plasticity of the brain and on behavior. By controlling for genetic variation in twins, we hope to understand the influence of environmental factors on brain and mental health. Since the genes of monozygotic twins are almost identical and those of dizygotic twins are 50% identical, we can draw conclusions about the interplay between genetic and environmental aspects. 

Consider a pair of identical twins who grew up together. At some point, the twins moved to different regions: one now lives in a big city, while the other has moved to the countryside. With this pair of twins, we can study how differences in environment lead to differences in behavior and/or brain, because their genetics and many aspects of their early life environment are the same.

More extended analysis includes family members, such as the parents, siblings, or children of twins. These complementary analyses help us even further to understand how environment exposure is transferred across generations and influences us over time. We are also interested in comparing twins with the rest of the population to ensure that we can transfer the findings to the general populace. 

Literature 

Bijnens, E. M., Derom, C., Thiery, E., Weyers, S., & Nawrot, T. S. (2020). Residential green space and child intelligence and behavior across urban, suburban, and rural areas in Belgium: A longitudinal birth cohort study of twins. PLOS Medicine, 17(8), e1003213. https://doi.org/10.1371/journal.pmed.1003213  

Cohen-Cline, H., Turkheimer, E., & Duncan, G. E. (2015). Access to green space, physical activity and mental health: a twin study. Journal of Epidemiology and Community Health, 69(6), 523–529. https://doi.org/10.1136/jech-2014-204667  

Plomin, R., DeFries, J. C., Knopik, V. S., & Neiderhiser, J. M. (2016). Top 10 replicated findings from behavioral genetics. Perspectives on Psychological Science, 11(1), 3–23. https://doi.org/10.1177/1745691615617439