Many young people experience depressive symptoms, and it is growing into a serious public health burden. Various studies suggest that environmental factors are related to depressive symptoms, including greenness, family, neighborhood, and so on. To get a more comprehensive view of the matter, a research team led by Professor Jaakko Kaprio used an exposome approach providing a holistic and expansive view of the environment.
The study, just published in the scientific journal Nature Mental Health, was based on the Finnish twin cohort, which is a large and nationwide research collecting data and samples from twins born in 1983-1987 and their teachers and families.
Researchers assessed Finnish twins twice, once at age 17 and once in young adulthood, and screened up to 385 environmental factors such as tree cover, satisfaction with parents, education level in the neighborhood, and so on. More than 3,000 individuals participated in both phases of the study.
The study identified 46 factors strongly connected with depressive symptoms at age 17 and 29 factors connected with depressive symptoms in young adulthood. Most of the exposures related to depressive symptoms are from the familial environment, such as the relationship between participants and their parents. For instance, a fair family atmosphere protects adolescents from more occurrences of depressive symptoms.
“Our findings also underscore the systematic and comprehensive investigation on mental health from the exposome framework”, says the lead author of the study, Zhiyang Wang from the Institute for Molecular Medicine Finland (FIMM), University of Helsinki.
Moreover, since identical twins share 100% of their genes and fraternal twins are genetically full-siblings, the researchers were able to estimate the importance of genetic factors on the relationship between the exposome and depressive symptoms. Genetics do influence both depressive symptoms and the exposures and environments experienced by participants, but most of the overlap between the exposome and depressive symptoms was environmental.
The results emphasize how our surroundings may impact depressive symptoms, as well as broader mental health, among youth and young adults. In studying the impact of the environment, the role of genetic susceptibility, which varies between people, needs to be accounted for to obtain a full understanding of which aspects of our lives may affect our risk for depressive symptoms.
The study was done in collaboration with the Barcelona Institute for Global Health and the National Institute for Public Health and the Environment in the Netherlands.
Wang, Z., Zellers, S., M. Whipp, A. et al. The effect of environment on depressive symptoms in late adolescence and early adulthood: an exposome-wide association study and twin modeling. Nat Mental Health (2023). https://doi.org/10.1038/s44220-023-00124-x