Controversy rages over whether the poor health suffered by some former soldiers is due to some form of poisoning, or is based in psychology.

Many have claimed they are ill as a result of exposure to organophosphates or the chemicals contained in injections designed to protect them from biological warfare methods.

But research published in the British Journal of Psychology suggests "flashbacks" caused by familiar sounds or smells are so deep rooted they have a pronounced, and genuine physical effect.

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Their research comes after another psychiatrist suggested a third of all war veterans may be in need of some psychiatric help.

The study team, led by psychologists Eamonn Ferguson and Helen Cassaday, at the University of Nottingham, suggests a combination of medical and psychological treatments might prove effective in some cases.

Body counter-attacks

They noticed some sufferers only experienced symptoms after experiencing sounds and smells they linked with the Gulf.

Their research suggests the familiar sound, smell or taste, for example the odour of diesel fumes, may provoke a strong psychological response.

As a result the body's immune system thinks the body is under attack, and launches a counter-attack that produces the debilitating symptoms.

The psychologists suggest drugs which damp down an immune response could lessen the physical effects of the psychological response.

Veterans have reported a wide variety of different symptoms, leading to suggestions Gulf War Syndrome may be a collection of different illnesses with different causes rather than a single one.

The symptoms include insomnia, fatigue, headaches, confusing, joint and muscle pain, nausea, swollen glands and fevers.

The other research, by Dr Nigel Hunt of Nottingham Trent University, published alongside a book of veteran's stories,called "Bloody Hell", revealed 36% of the 709 veterans he surveyed fulfilled the criteria for possible psychiatric cases.

The survey showed 'flashbacks' and 'reliving' combat horrors happens decades after the actual events.