Duke University study finds genetic link between poverty and an increased risk of depression

The study reveals a new biological pathway for depression in adolescents.

The study, released today by Molecular Psychiatry, represents some of the first research to examine changes in epigenetic markers in individuals over time and relate this to changes in brain function. 132 Caucasian adolescents from households that ranged from low to high socioeconomic status were involved in the study, with the results revealing that even moderately lower socioeconomic status caused biological differences that elevate the risk for depression. The lead author of the study, Johnna Swartz, talked to us about what her results could mean for the treatment and prevention of depression.

RG: Could you explain the findings of your study and their significance?

Johnna Swartz: In this study, we identified a pathway through which low socioeconomic status may increase risk for the future development of depression by altering the way genes are expressed and the way the brain processes information. Specifically, we found that adolescents growing up in households with lower socioeconomic status have increased epigenetic markers near a gene that has previously been associated with depression, which may affect how the gene is expressed. We also found that having more of these epigenetic markers was associated with increased activity in a brain region, the amygdala, that plays a critical role in the stress response and has also been linked to depression.

Finally, we found that increased amygdala activity in adolescents predicted the future emergence of depression symptoms more than one year later, particularly for adolescents who had a parent or sibling with a history of depression.

RG: What method did you use to reach these results?

Swartz: We used a combination of techniques. Bisulfite pyrosequencing was used to measure the epigenetic markers near our gene of interest: the serotonin transporter gene. We used functional magnetic resonance imaging to measure activity in the amygdala when adolescent participants viewed threatening faces.

RG: What do your findings mean for the treatment and potential prevention of depression?

Swartz: This work is still very much in its early stages, but a long-term goal of this research is to identify markers that can help us predict who might be at greater risk for developing depression and understand the specific biological pathways leading to that risk. Depression is a heterogeneous disorder, so understanding the biological pathways involved for an individual may help us predict the course of the disorder or how that individual will respond to different treatments.

RG: Is there anything that families with low socioeconomic backgrounds can do to mitigate the risk of depression?

Swartz: It’s too early to know what specific mechanisms may be associated with the changes in epigenetic markers and brain function we observed in this sample –  we plan on replicating this finding and identifying potential risk factors that may be associated with this effect.

However, we have some hypotheses regarding certain risk factors that may be affecting these biological markers.  For example, smoking during pregnancy, increased stress exposure, and certain diets have been linked to changes in epigenetic markers across different genes. We plan to look into these risk factors, along with others, to identify targets to change that might mitigate risk.

RG: What lead you to study the biological link between poverty and depression?

Swartz: Low socioeconomic status is a well-known risk factor for depression and unfortunately affects a large number of families within the United States and worldwide. Previous research had also shown that low socioeconomic status in childhood affects the expression of other genes linked to depression. We therefore hypothesized that it might be associated with the biological pathway we examined in the present study.

RG: What’s the next step in this research?

Swartz: There are several different directions we’re pursuing to continue this research. As mentioned above, we’re interested in identifying the specific risk factors present in families with low socioeconomic status that may affect epigenetic markers and brain function. We’re also interested in identifying additional genetic, epigenetic, and brain markers that can help us better predict which individuals are at highest risk for depression.

Additionally, we’re planning on following the participants of the present study into young adulthood to test whether these epigenetic and brain markers predict the development of clinical depression, as well as other problems such as alcohol or substance abuse.

RG: What can we learn about the biological influencers of depression from your results?

Swartz: I think one aspect of this research that’s exciting is that it suggests that our biology is not necessarily fixed from an early age. This opens the possibility that perhaps our biology can change for the better given positive environmental contexts. This is an area of research that we plan to continue to pursue moving forward.

Image courtesy of Ryan Melaugh.