Low levels of a specific biomarker in your blood may be linked to the severity and duration of depression.
Researchers from Stanford and Rockefeller universities conducted a series of experiments on rodents.
Finding a deficiency in the biomarker known as acetyl-l-carnitine was connected to more behaviors related to depression.
Then in a separate study, the team examined patients diagnosed with depression.
Finding these people also had lower levels of this biomarker in their blood. The lower the levels of this in their bloodstream, the more severe case of depression they had.
Researchers said more work is needed to determine whether a supplement may improve symptoms.
The study was published online July 13 ahead of being printed in the journal "Proceedings of the National Academy of Sciences."