Genetic risk for depression predicts financial struggles, but the cause isn’t what scientists thought

A new study published in the Journal of Psychopathology and Clinical Science offers a nuanced look at how genetic risk for depression interacts with social and economic life circumstances to influence mental health over time. The findings indicate that while people with a higher genetic liability for depression often experience financial and educational challenges, these challenges may not be directly caused by the genetic risk itself.

Scientists conducted the study to better understand the developmental pathways that lead to depressive symptoms. A major theory in psychology, known as the bioecological model, proposes that genetic predispositions do not operate in a vacuum. Instead, this model suggests that a person’s genetic makeup might shape the environments they select or experience. For example, a genetic tendency toward low mood or low energy might make it harder for an individual to complete higher education or maintain steady employment.

If this theory holds true, those missed opportunities could lead to financial strain or a lack of social resources. These environmental stressors would then feed back into the person’s life, potentially worsening their mental health. The researchers aimed to test whether this specific chain of events is supported by data. They sought to determine if genetic risk for depression predicts changes in depressive symptoms specifically by influencing socioeconomic factors like wealth, debt, and education.

To investigate these questions, the researchers utilized data from two massive, long-term projects in the United States. The first dataset came from the National Longitudinal Study of Adolescent Health, also known as Add Health. This sample included 5,690 participants who provided DNA samples. The researchers tracked these individuals from adolescence, starting around age 16, into early adulthood, ending around age 29.

The second dataset served as a replication effort to see if the findings would hold up in a different group. This sample came from the Wisconsin Longitudinal Study, or WLS, which included 8,964 participants. Unlike the younger cohort in Add Health, the WLS participants were tracked across a decade in mid-to-late life, roughly from age 53 to 64. Using two different age groups allowed the scientists to see if these patterns persisted across the lifespan.

For both groups, the researchers calculated a “polygenic index” for each participant. This is a personalized score that summarizes thousands of tiny genetic variations across the entire genome that are statistically associated with depressive symptoms. A higher score indicates a higher genetic probability of experiencing depression. The researchers then measured four specific socioeconomic resources: educational attainment, total financial assets, total debt, and access to health insurance.

In the initial phase of the analysis, the researchers looked at the population as a whole. This is called a “between-family” analysis because it compares unrelated individuals against one another. In the Add Health sample, they found that higher genetic risk for depression was indeed associated with increases in depressive symptoms over the 12-year period.

The data showed that this link was partially explained by the socioeconomic variables. Participants with higher genetic risk tended to have lower educational attainment, fewer assets, more debt, and more difficulty maintaining health insurance. These difficult life circumstances, in turn, were associated with rising levels of depression.

The researchers then repeated this between-family analysis in the older Wisconsin cohort. The results were largely consistent. Higher genetic risk predicted increases in depression symptoms over the decade. Once again, this association appeared to be mediated by the same social factors. Specifically, participants with higher genetic risk reported lower net worth and were more likely to have gone deeply into debt or experienced healthcare difficulties.

These results initially seemed to support the idea that depression genes cause real-world problems that then cause more depression. However, the researchers took a significant additional step to test for causality. They performed a “within-family” analysis using siblings included in the Wisconsin study.

Comparing siblings provides a much stricter test of cause and effect. Siblings share roughly 50 percent of their DNA and grow up in the same household, which controls for many environmental factors like parenting style and childhood socioeconomic status. If the genetic risk for depression truly causes a person to acquire more debt or achieve less education, the sibling with the higher polygenic score should have worse economic outcomes than the sibling with the lower score.

When the researchers applied this sibling-comparison model, the findings changed. Within families, the sibling with higher genetic risk did report more depressive symptoms. This confirms that the genetic score is picking up on a real biological vulnerability. However, the link between the depression genetic score and the socioeconomic factors largely disappeared.

The sibling with higher genetic risk for depression was not significantly more likely to have lower education, less wealth, or more debt than their co-sibling. This lack of association in the sibling model suggests that the genetic risk for depression does not directly cause these negative socioeconomic outcomes. Instead, the correlation seen in the general population is likely due to other shared factors.

One potential explanation for the discrepancy involves a concept called pleiotropy, where the same genes influence multiple traits. The researchers conducted sensitivity analyses that accounted for genetic scores related to educational attainment. They found that once they controlled for the genetics of education, the apparent link between depression genes and socioeconomic status vanished.

This suggests that the same genetic variations that influence how far someone goes in school might also be correlated with depression risk. It implies that low education or financial struggle is not necessarily a downstream consequence of depression risk, but rather that both depression and socioeconomic struggles may share common genetic roots or be influenced by broader family environments.

The study has some limitations. Both datasets were comprised almost entirely of individuals of European ancestry. This lack of diversity means the results may not apply to people of other racial or ethnic backgrounds. Additionally, the measures of debt and insurance were limited to the questions available in these pre-existing surveys. They may not have captured the full nuance of financial stress.

Furthermore, while sibling models help rule out family-wide environmental factors, they cannot account for every unique experience a person has. Future research is needed to explore how these genetic risks interact with specific life events, such as trauma or job loss, which were not the primary focus of this investigation. The researchers also note that debt and medical insurance difficulties are understudied in this field and deserve more detailed attention in future work.

The study, “Genotypic and Socioeconomic Risks for Depressive Symptoms in Two U.S. Cohorts Spanning Early to Older Adulthood,” was authored by David A. Sbarra, Sam Trejo, K. Paige Harden, Jeffrey C. Oliver, and Yann C. Klimentidis.