Heard of worrying yourself sick? Scientists have found that people can literally age themselves with depression, BBC News reported.

A study with findings from more than 2,000 people found that cells looked biologically older for those who were severely depressed or had been in the past. Published in Molecular Psychiatry, researchers couldn't explain the differences in cell ageing through other factors like smoking.

Scientists measure cell ageing through something called telomere length, according to BBC.

Josine Verhoeven from the VU University Medical Centre in the Netherlands, along with colleagues from the US, put together the report. In the study, one-third of the participants were currently depressed, one-third had experienced severe depression in the past and the remaining third had never battled depression.

The volunteers gave a blood sample to be analyzed by researchers, who were "looking for changes in structures deep inside cells called telomeres," according to BBC.

Measuring the length of telomeres is a way to calculate the age of cells, since telomeres grow shorter as cells divide. Capping the end of chromosomes, the telomere's role is to stop any unwanted loss of DNA.

The difference between people who were or had been depressed was still evident even after lifestyle factors like heavy drinking or smoking were taken into account. People who had struggled with depression had significantly shorter telomeres than those who had never been depressed.

The participants who had been severely and chronically depressed had the shortest telomeres. Researchers speculated that shortened telomeres signify the body's reaction to distress caused by depression.

"This large-scale study provides convincing evidence that depression is associated with several years of biological ageing, especially among those with the most severe and chronic symptoms," researchers said.

What is less certain is whether or not shortened telomeres are harmful.

Telomere length doesn't necessarily predict death risk, according to Dr. Anna Phillips of the University of Birmingham, who has studied the effects of stress on telomere length.

It is also likely that mild-to-moderation depression doesn't affect telomere length, which is probably only related to major depressive disorders, she said.

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