Scientists have discovered that aging immune cells may hold a hidden blood-based clue to detecting depression.

Scientists have discovered that the biological aging of certain white blood cells may provide an important clue to depression, potentially opening the door to a blood test that could help identify the condition.

The study found that measuring how quickly these immune cells age can help predict emotional and cognitive symptoms of depression, including hopelessness and loss of pleasure. Interestingly, the same biological markers were not associated with physical symptoms such as fatigue or changes in appetite.