Researchers have found that adversity or mental disorders faced by children and teenagers can cause biological changes, such as a shortening of telomeres - protein caps at the ends of our chromosomes that control how quickly a cell ages - and alterations to the mitochondrial DNA, both of which are linked to the natural ageing process. This suggests that a person's biology and experiences could together contribute to their susceptibility to age-related disease.
Mitochondria play a crucial role in how our cells grow, differentiate, replicate, and die, and when we age, our mitochondrial energy production and function declines, and mitochondrial DNA (mtDNA) content increases to compensate for this dysfunction, allowing mutations to accumulate. This increase in mutations can lead to a number of deadly age-related disorders such as cardiovascular disease, diabetes, and some forms of cancer.
Similarly, as we age and our cells replicate, the chromosomes within shed mutiple DNA sequences, and it's our telomeres' job to ensure that nothing too critical is being lost. But our telomeres grow shorter and shorter with every cell division, so as we age, we grow more susceptible to disorders such as cardiovascular disease, diabetes, stroke and autoimmune conditions.
Research has shown that stress can lead to accelerated shortening of the telomeres, and mental disorders have been linked to mitochondrial dysfunction. But until now, no studies have examined the relationship of mitochondrial DNA to psychosocial stress, which relates to a person's psychological development in, and interaction with, a social environment.
"We are interested in these relationships because there is now clear evidence that stress exposure and psychiatric conditions are associated with inflammation and health conditions like diabetes and heart disease," Audrey Tyrka, director of the Laboratory for Clinical and Translational Neuroscience at Butler Hospital and associate professor of psychiatry and human behaviour at Brown University in the US, said in a press release. "Identifying the changes that occur at a cellular level due to these psychosocial factors allows us to understand the causes of these poor health conditions and possibly the overall ageing process."
The team worked with 290 heathy adult volunteers (177 women and 113 men) who were assessed on whether they were affected by various psychosocial disorders when they were kids, such as anxiety and depression, or experienced any major childhood adversities, for example, the loss of a parent, a lack of proper care, or abuse. The volunteers were divided into four groups - those who had experienced childhood adversity; those who hadn't; those who had been affected by depressive, anxiety, or substance use disorders; and those who hadn't. They then submitted blood samples and had their telomere length and mtDNA copy number measured, the latter commonly used to determine a person's mitochondrial DNA content.
The researchers found that not only did the adults with stressful childhood experiences have shorter telomeres than those who didn't, but they also had increased mtDNA content, and this combination could be putting them at higher risk of developing age-related diseases.
"Childhood adversity and lifetime psychopathology were each associated with shorter telomeres and higher mtDNA copy numbers," the researchers reported in the journal Biological Psychiatry. "Significantly higher mtDNA copy numbers and shorter telomeres were seen in individuals with major depression, depressive disorders, and anxiety disorders, as well as those with parental loss and childhood maltreatment. A history of substance disorders was also associated with significantly higher mtDNA copy numbers."
Tyrka admits that they're not exactly sure how psychological stress can actually alter a person on a physical, cellular level, but says this is an important area for more study, because it could help us figure out how to better those affected by it. "Understanding this biology is necessary to move toward better treatment and prevention options for stress-related psychiatric and medical conditions, and may shed light on the ageing process itself," she said.