For years, depression has been thought of as a mental condition but a growing number of scientists now think it could be more of a physical condition similar to an allergy.

George Slavich, a clinical psychologist at the University of California in Los Angeles, has come out saying he believes depression is more of a physical illness than a mental one. He says ‘It does involve psychology, but it also involves equal parts of biology and physical health’.

This theory came about after studying people who were ill and consequently felt generally miserable. The feeling of being unable to do anything while ill are very similar to typical symptoms of depression. There are reasons we feel tired and lethargic when we are ill. It is mainly to stop us going out and overexerting ourselves, potentially causing more damage to our bodies.

So the question is, if people with depression show classic ‘sick symptoms’ and people who are sick show classic signs of depression, are the two linked?

The similarity between the two has lead scientists to think that both may be caused by ‘inflammation’, a part of the immune system that acts as a protection against illness, and is set off by a family of proteins called cytokines, which switches the brain into sickness mode.

In the past. Cytokines and inflammation have been shown to dramatically increase during depression, and also in people with bipolar, while decreasing in periods when the illness is not seriously affecting a sufferer’s life.

So what causes the inflammation?

It is thought by scientists that a diet rich in trans fats and sugar has been shown to promote inflammation, while a healthy one full of fruit, veg and oily fish helps keep it at bay.

People who are clinically obese also show are at risk of inflammation as large quantities of cytokines are stored round the fatty areas of the body, particularly the belly.

Another interesting cause of inflammation is stress, in particular stress caused by social rejection and loneliness.

Taking the above points into account, it could be seen that depression is a modern day allergy which increases the more we eat, slob and isolate ourselves from social activities.

There is also evidence that omega 3 and curcumin, (an extract of the spice turmeric), may be beneficial in reducing inflammation in the body which could lead to an improvement in the symptoms of depression. Although these are thought to improve the symptoms, they should not be thought of as a replacement to other treatments prescribed by doctors.

In between five to 10 years, says Carmine Pariante, a psychiatrist at Kings College London, there may be a blood test that can measure inflammation in people with depression so that they can be treated accordingly. Researchers have already come up with a simple finger-prick test that reliably measures inflammation markers in a single drop of blood.