New research published in Nature Mental Health revealed significant genetic and environmental associations with depressive symptoms.
Western Europe has been witnessing a high prevalence of Major Depressive Disorder, with an alarming rise among adolescents. The COVID-19 pandemic exacerbated this trend. In this work, Wang Zhiyang and colleagues consider the entirety of one’s environmental exposures (termed “exposome”) as well as relevant genetic factors, to better understand vulnerabilities to depression.
The researchers utilized the FinnTwin12 cohort dataset, which included twins born in Finland between 1983-1987. Of this sample, 3025 participants were in young adulthood (with a mean age of approximately 22 years), and 4127 participants were at age 17. The researchers employed two key methods, including Exposome-wide Association Studies (ExWAS) and bivariate twin modeling. The first is similar to genome-wide association studies with a focus on environmental factors instead of genetic variations. The latter allows for the decomposition of trait variability into additive and dominant genetic components, as well as common and unique environmental components.
The researchers considered 385 environmental exposures and grouped them into 12 domains. Some of these included air pollution, family dynamics, and life events. They further considered factors such as parental education and work status as potential confounding variables.
In the ExWAS, Zhiyang and colleagues identified 29 exposures as significantly associated with depressive symptoms in young adulthood, and 46 exposures at age 17, spanning 12 distinct environmental domains. Most notably, familial exposures emerged as the most influential factors, highlighting the significant impact of family dynamics and relationships in the development and persistence of depressive symptoms during late adolescence and early adulthood.
However, none of these exposures were associated with the incidence of Major Depressive Disorder in young adulthood. Further, environmental effects had a greater impact than genetic effects in males than females.
Bivariate twin modeling revealed a complex link between genetic, environmental factors, and depressive symptoms, showing that while both genetic and environmental factors significantly contribute to the variance in depressive symptoms, genetics has a slightly larger influence. Environmental factors, as part of one’s exposome, are closely associated with genetic aspects. Family influences, such as happiness levels or domestic issues, can be passed down through genes and shared family environments.
This finding highlights the importance of understanding how genes and one’s environment interact and affect the way in which certain genetic traits can lead to different health outcomes depending on the environment.
A limitation the researchers note is that compared to other ExWAS research, the sample utilized in this work is relatively small. Thus, they were unable to stratify the data by sex as it would reduce the sample size by half.
The study, “The effect of environment on depressive symptoms in late adolescence and early adulthood: an exposome-wide association study and twin modeling”, was authored by Wang Zhiyang, Stephanie Zellers, Alyce M. Whipp, Marja Heinonen-Guzejev, Maria Foraster, Jordi Júlvez, Irene van Kamp, Jaakko Kaprio.
