A new study suggests that the environmental influence of parents’ genes, known as genetic nurture, may have a small influence on traits like depression and neuroticism in their offspring. The findings have been published in JAMA Psychiatry.
The researchers, Justin D. Tubbs and Pak C. Sham, conducted their new study to better understand the genetic and environmental factors that contribute to clinical depression, a significant public health burden affecting millions of people worldwide. They were particularly interested in examining the concept of genetic nurture, which refers to the effects of parental genes on their children’s traits beyond the direct genetic inheritance.
For example, a child may inherit certain genes that increase their risk for depression from their parents. However, the parents’ own genetically-influenced traits, such as their personality or mental health, can also affect the child’s environment. In this case, the parent’s genetic makeup is indirectly impacting the child’s traits by influencing how they raise and interact with the child.
“While most people are familiar with the idea of genetic factors (‘nature’) and environmental factors (‘nurture’) contributing to traits and risk for disease, these sources are often difficult or impossible to disentangle accurately without certain types of data and appropriate methodology,” explained Tubbs, a post-doctoral research fellow at Massachusetts General Hospital.
“Although many epidemiological studies have found associations between certain traits or behaviors in parents with increased risk of depression in their children, very few of these studies consider genetics as a potential confounding factor that could partially explain their findings. On the other hand, when genetic researchers perform large genome-wide association studies of depression in samples of unrelated individuals, the signals they detect are often assumed to be entirely genetic.”
“Therefore, our paper focused on understanding the potential for ‘genetic nurture’ to bias results from genetic studies of depression (although our methods can also be applied to a wide range of other traits).”
To conduct the study, the researchers used data from the UK Biobank, which is a large population-based sample with detailed genetic and phenotypic information. They focused on nuclear families of White British ancestry, excluding individuals who were adopted, to ensure a clear connection between parents and offspring. The final sample included 38,702 individuals.
Tubbs and Sham used advanced genetic methods, including genotype imputation and polygenic scoring, to estimate the contribution of genetic nurture to offspring depression and neuroticism. Polygenic scores are a way of summarizing the influence of multiple genetic variants associated with a trait.
The results of the study revealed evidence of a statistically significant association between genetic nurture and lifetime depression and neuroticism in adults. The researchers found that genetic factors passed on from parents explained a small proportion of the variance in offspring depression and neuroticism. However, the offspring’s own genetic factors had a more significant impact on these traits.
In other words, the findings suggest that genetic nurture may have a small impact on depression and neuroticism, but it is not as significant as the genetic factors passed directly from parents to children.
“Complex traits can never be boiled down to either purely ‘nature’ or purely ‘nurture.’ Without careful modeling and interpretation, sometimes environmental effects can be misinterpreted as genetic effects and vice-versa,” Tubbs told PsyPost.
“Overall, our work supports the view that genes have far-reaching effects. A person’s genes have important influences not only on the individual’s own health and outcomes, but can also have significant effects, through the person’s behaviors or other attributes, on significant others including family and friends.”
“We found preliminary evidence that many genetic studies of depression may be capturing both genetic and environmental influences when they estimate the association between polygenic scores and depression,” Tubbs added. “Additional studies of relatives will be necessary to confirm these findings and accurately disentangle the influences of genes and environment.”
The study, “Preliminary Evidence for Genetic Nurture in Depression and Neuroticism Through Polygenic Scores“, was published June 7, 2023.
