Around one in five Britons suffer from depression at some point in their lives / PA

Study is a major step towards understanding disease

Depression could be diagnosed by a blood test, according to newly published American research, which has found chemicals in the blood of people with the condition.

Presently, depression is diagnosed through a lengthy consultation with doctors and is based on mood and screening tests using questionnaires.

Scientists at Chicago’s Northwestern University claim they have identified nine chemicals in the blood which are raised during depression in a small complex study.

Dr Cosmo  Hallström, a Fellow of the Royal College of Psychiatrists, said of the trials: “They have come up with a battery of tests that look promising”.

“It’s good the work is being done,” he told The Independent. “There is a strong push at the moment to discover if there are biological determiners for depression.”

Finding a ‘biological determiner’ of depression could also demonstrate that the condition is a disease and not simply the result of particularly sad events.

“If you can perform blood tests then you can distinguish between patients who are depressed through circumstances and those whose illness perhaps has a biological root or determiner,” he said.

However, Dr Hallström noted the signs for adult depression are highly recognisable to professionals, suggesting the value of the research may lie more in “targeted treatment”, allowing doctors to better help those suffering.

In this way, patients who were identified as suffering from depression as a result of ‘biological determiners’ could be treated with medication, while depression brought on by tragic circumstances could be alleviated by different methods, such as more conventional therapy.

The tests, conducted on 14 teenagers suffering from severe depression and 14 who were not suffering from any kind of depression, measure three of these chemicals in order to diagnose depression.

Early onset major depression has worse prognosis than the adult onset condition and affects up to 25 per cent of people in their late teens.

Co-author of the study Eva Redei said the chemicals in the blood could be interpreted as a ‘neurodegenerative fingerprint’ indicating future problems.

Writing in the journal Translational Psychiatry, Ms Redei said: “The pilot data presented here suggest that our approach leads to a clinically valid diagnostic panel of blood transcripts that can differentiate early-onset major depressive disorders from controls.”

She added that plans to extend the tests needed to be undertaken, but results could show that measuring blood chemical levels may be a useful way to check treatment is working.

Around one in five Britons suffer from depression at some point in their lives, but a small number suffer from clinical depression – a condition which can cripple an individual’s life for weeks and sometimes years.