On 24th May, a team of researchers from Duke University published a research paper about depression titled “An epigenetic mechanism links socioeconomic status to changes in depression-related brain function in high-risk adolescents”.

The research findings were also published by Molecular Psychiatry-Nature, which aimed at highlighting the underlying biological variables that contributed towards psychiatric disorders.

With the surfacing of this research, a step forward has been taken in understanding depression, in connection with socio-economic status and epigenetic changes in the brain. The findings of the research suggested that an epigenetic change in a gene increases amygdala activity which makes a person prone to suffering from the heavy-heartedness caused by this condition.

Lead researcher Johnna Swartz said, “This is some of the first research demonstrating that low socioeconomic status can lead to changes in the way genes are expressed, and it maps this out through brain development to the future experience of depression symptoms.”

For a long time, this melancholy-inducing condition has been assumed to be associated with poverty, living conditions and daily struggles throughout a person’s life. But no concrete evidence of underlying biological changes in this regard has been previously presented. The study from Duke University, being the first in this respect, has opened up avenues for further research in finding biomarkers of depression and offering personalized treatments to patients.

This study was conducted over a period of three years in which participants were adolescents coming from a range of socioeconomic backgrounds.

Socioeconomic status (SES) is a comprehensive way of categorizing people based on their education, earning and occupation. A person’s social standing amidst a population was hypothesized to be linked with their likelihood of developing depression over a course of time. For this very purpose, a comparison had to be made between the brain activities of adolescents coming from high and low SESes.

A total of 132 non-Hispanic Caucasians adolescents between the ages 11-15 were included in the study. These participants were a part of Teen Alcohol Outcomes Study (TAOS). Amongst these participants, half of them came from families that had a history of depression.

Family history has been seen as the biggest contributor to depression, and therefore the study found a need to have participants with a family history of depression to obtain conclusive findings. Brain scans though neuroimaging, genetic analysis and behavioral changes were the variables under observation for this study.

Interestingly, this team had previously found amygdala from functional magnetic resonance imaging (MRI), to be directly involved in the incidences of depression and anxiety. The experts found that an increased activity in the amygdala can be a prime factor in developing depression over the years. Prior to the manifestation of symptoms of depression, if MRI scans indicate increased amygdala activity, it can be inferred that the person is at a high risk of developing depression in the near future.

What Is Amygdala?

Amygdala is an almond shape of nervous tissues that is located in the temporal lobe of the brain. A human has two amygdalae, one in each hemisphere. Amygdala is assumed to be a part of the brain’s limbic system which controls emotions, memory and survival instincts of a person.

However, another fraction of experts argue that the amygdala is not a part of the limbic system and it works independently. Nevertheless, it is unanimously agreed that the amygdala detects stressors and fear from the environment whilst preparing a response to fight off these fears.

This finding led the experts to observe increased amygdala activities in the brains of adolescents and see if any corresponding link to likelihood of developing depression could be made.

A year after the conclusion of the 2014 study, the participants who were now aged 14-19, were asked for any manifestation of depression symptoms. Adolescents, particularly with a family history of depression, were reported to have experienced symptoms of depression. This further fortified the link between amygdala activity and an increased risk of suffering feelings of hopelessness and dreariness.

In addition to this, the epigenetic changes in gene — gene linked with depression — were evidently found to be present in adolescents coming from low SES families. In participants from low SES backgrounds, it was observed that over a period of two years, increased quantities of the chemical tag were accumulated on depression-linked genes. These chemical tag accumulations were bringing about epigenetic changes primarily through DNA methylation in the target gene, which resulted in increased responsiveness in the amygdala. The aberration caused by these epigenetic changes was pronounced upstream of the gene SLC6A4 gene.

What Is The Role Of SLC6A4 Gene In Depression?

The SLC6A4 (solute carrier family 6 member 4) gene is responsible for producing an integral membrane protein that is an essential transporter of the neurotransmitter, serotonin, across synapse. A mutation in the SLC6A4 gene can affect the serotonin uptake of neural cells. Low serotonin levels have long been associated with an increased risk of depression and anxiety.

But with this latest study from Duke University, a link between epigenetic changes of SLC6A and responsiveness of amygdale has been established. This will lead to scientists looking for an increased number of biomarkers and interactions between different genes, in whole genome sampling, in an attempt to unravel underlying, unexplored genetic risk factors of this gloom-inducing condition.

In this context, more longitudinal studies on a larger scale have to be conducted to look at the genetic change that is brought in a person over time.

According to an estimate by the World Health Organization (WHO), 350 million people suffer from depression globally. As it is one of the biggest contributors towards the burden of mental disorders, researchers work tirelessly to understand depression better. The results from this study will help reach a milestone for categorizing depression cases based on the environmental and biological causes.

With  an improved diagnosis, the degree of the condition will be better evaluated, which will in turn, help health professionals in formulating individualized prevention strategies for people who have fallen prey to such despondency.