It’s well known that stress and depression go hand in hand. But could science provide a way to predict depression?
Right now, clinicians have to rely on detecting depression using a series of psychological tests and interviews, which are subject to a wide degree of variability.
Researchers are currently looking for biomarkers, or signs within the body, that could indicate whether someone is truly depressed or at-risk for developing depression.
A collaboration between the University of Oxford in the United Kingdom, Hua Shan Hospital at Fudan University in China, and the Virginia Commonwealth University in the United States may have found one such biomarker.
The team surveyed 11,670 women, half of whom experienced major depression and half of whom did not. They collected DNA samples from each of the women as well as information about their history of stressful life events.
The researchers discovered that the more severe the events were, the higher the rates of depression among the women. Also, consistent with previous research, higher rates of stress were associated with shorter telomeres, the caps on the ends of DNA strands that protect them from deterioration when cells divide.
The telomere gets shortened every time the cell replicates, so its length determines the lifespan of the cell. Shortened telomeres among people who have experienced stress may partially explain why stress contributes to so many different diseases throughout the body.
The team also found a second biomarker: increased levels of DNA from mitochondria (mtDNA), small structures inside of cells that produce energy.
Looking closer, they also found that these two biomarkers were associated not independently as a result of stress but rather of stress-induced depression. Among women without depression, even in the case of severe stress like childhood sexual abuse, telomere lengths and mtDNA levels were normal.
“We think that the increase in the amount of mtDNA and shortening of telomere is a consequence of stress,” said Jonathan Flint, professor of neuroscience at the University of Oxford and principal investigator of the research, in an interview with Healthline. “In some people, one of the consequences of stress is depression. We think that in this case, the molecular changes are more pronounced or maybe prolonged. There appear to be differences between people who do and do not go on to develop depression so it is possible that the markers might be clinically useful.”
The Story Is in the DNA
Most people who experience life stresses don’t go on to develop depression. The Centers for Disease Control and Prevention (CDC) found that nearly 64 percent of Americans have dealt with at least one major stressful event during childhood, such as enduring abuse or witnessing violence, and 3.7 percent of American adults have experienced serious psychological stress in the past month.
But despite these high numbers, only about 17 percent of Americans will experience major depression within their lifetimes.
Therefore, a biomarker to indicate who will, or has, become depressed would be invaluable.
To validate their findings, the team exposed a group of mice to different stresses, such as electric shocks or forcing them to swim, for four weeks. The animals also developed the same biomarkers, as did another group of mice that were dosed with stress hormones directly. However, once they were allowed to rest for another four weeks, their biomarkers returned to normal.
This finding offers hope to people who have experienced major life stresses and recovered from them. However, the sterile, controlled experiences subjected upon lab rats don’t bear a great resemblance to the complexity of human experiences.
“People who experienced stress in the past, particularly childhood severe stress such as sexual abuse, tend to have repeated episodes of stress later in life,” explained Flint. “Possibly also, they are primed to react more strongly to milder stress. We don’t know this yet.”
Even if the biomarker can’t be reversed in humans, it still may prove useful for diagnostics.
“We hope that it will be clinically useful and we hope it will tell us something about the biology of depression,” Flint concluded.