A blood test has been developed that can diagnose clinical depression by identifying low levels of a chemical in the body that boosts energy.d Picture: Pexels

 A blood test has been developed that can diagnose clinical depression by identifying low levels of a chemical in the body that boosts energy.
Scientists found people suffering with depression have lower readings for acetyl-L-carnitine (LAC), and the less of it they have, the more severe their symptoms and the earlier in life the illness is likely to strike.

LAC is sold as a fitness supplement, and may be important in fighting off depression because it prevents nerve cells over-firing in the brain’s hippocampus and prefrontal cortex - two regions where mood is controlled.

In studies, giving rodents the supplements reversed signs of depression within a few days.

But researchers led by Rockefeller University, a biomedical research institute in the US, say it is too early to advise people with depression to take the supplement until clinical trials are carried out.

The scientists compared LAC levels in the blood of 71 people with depression - 28 with moderate and 43 with severe depression - and 45 healthy people.

In men and women, those with depression had lower levels of the chemical.