A genetic predisposition towards obesity can increase stress in early life, which may make people more likely to develop depression in adulthood, a new study suggests.
The study, “A Polygenic Score for Body Mass Index is Associated with Depressive Symptoms via Early Life Stress: Evidence for Gene-Environment Correlation,” was published in the Journal of Psychiatric Research.
Overweight people can often be the target of bullying from peers, and subject to bias from healthcare providers, educators, and even parents and other family members. When this kind of behavior is targeted at children, it contributes to early life stress (ELS), which, in turn, can predispose them to mental health problems in adulthood.
Based on these associations, the researchers behind the new study predicted that people with a genetic predisposition towards having a high body mass index (BMI, a ratio of weight to height) would also be predisposed to higher ELS and future depression.
The researchers recruited 524 college students (average age of 19.8 years, 53% female, 100% white students). All subjects were genotyped, their ELS was assessed with the Childhood Trauma Questionnaire (CTQ), and their current state of depression was measured with the Center for Epidemiologic Studies Depression Scale (CES-D).
To construct a genetic BMI score, the researchers used genetic variants that previous studies had shown to be linked to BMI, which was also confirmed to be linked to BMI in their cohort. Then, they looked for statistically significant associations between this score and CTQ and CES-D scores, while accounting for variables such as sex and age.
Interestingly, genetic BMI scores were significantly associated with CTQ scores, and CTQ scores were significantly associated with CES-D scores — but genetic BMI and CES-D scores weren’t significantly associated. In other words, genetic BMI scores appeared to influence depression by affecting ELS.
The researchers replicated these findings using data from 5,930 people (average age of 62.7 years, 53% female, 100% white subjects) using the UK Biobank. Although ELS and adulthood depression were measured differently than in their previous study, the same link was found between them, suggesting that this association pattern is consistent across varied groups. However, the researchers noted that their findings are limited to populations of European descent and to the Western culture. Therefore, further studies will be needed to examine this association in different sociocultural contexts, they said.
These results suggest that having a genetic predisposition towards obesity increases the chance that a person will be exposed to high stress in early life — presumably because of bullying and stigma — which, in turn, increases the likelihood of depression in adulthood.
Thus, these “findings further encourage weight stigma-reduction efforts, specifically among family members and parents,” the researchers said.