Doctors at the Gulf war illness research unit at Guy's, King's and St Thomas's School of Medicine in London have today published research in the British Medical Journal which indicates that self-reported ill-health among veterans of the conflict cannot be fully explained by mental illness.

Campaigners have said this vindicates their belief that physical problems are not "just in the minds" of sufferers.

The five-year-long research involved questioning 12,000 British veterans from the 1990-91 Gulf war and the 1992-97 Bosnian peace mission and comparing results.

The unit's director, Simon Wessely, said: "The Gulf war veterans did have slightly raised levels of post-traumatic stress disorder and depression, but they were nothing like sufficient to explain the far greater intensity of their physical complaints."

Mr Wessely, who declined to call the illness a syndrome because the physical ailments of the veterans were no different from other conflicts, said that the number and intensity of complaints was up to three times higher. "Our findings show that this is not due to a psychological disorder," he told Reuters.

The research found that only 24% of the Gulf war veterans who reported a physical disability also had a psychiatric disorder - a similar percentage to the veterans of other conflicts. In non-disabled Gulf war veterans the rate of psychiatric disorders fell to 12%.

The first stage of the project, published in January 1999, showed that Gulf war veterans were up to twice as likely to report sick than soldiers who had been posted to Bosnia and three times more likely to do so than those who had been posted to other areas.

What was the response of veterans' groups to the findings?

The National Gulf Veterans and Families Association (NGVFA) welcomed the findings, but again called for a public inquiry, arguing this was imperative as Britain was on the "eve" of a second Gulf war.

Former paratrooper Shaun Rusling, chairman of the group, said: "Eleven years after the first Gulf war we are no clearer to an explanation of what happened to servicemen. Our troops who will be exposed to the same as we were 11 years ago need to know that should they be ill or injured that they will get the best medical care and proper pensions."

What is believed to be causing the illness?

In June, NGVFA gave evidence at a US congressional subcommittee on national security hearing in Westminster saying that tests on veterans have found traces of depleted and enriched uranium in their blood and urine. Depleted uranium was used by the Ministry of Defence (MoD) in "tank-busting" missiles during the Gulf war.

Many of the men affected were involved in clean-up operations following Desert Storm in 1991. Illnesses among more than 5,000 British veterans have also been linked to powerful immunisation tablets given to soldiers to protect them from chemical attack, and the use of corrosive organophosphates to try to keep down disease.

Campaigners for Gulf veterans want a public inquiry into the illnesses, which are sometimes described as Gulf war syndrome, or post-traumatic stress disorder (PTSD). MoD doctors have denied in the past that there is any Gulf war disease, and no government has acknowledged it exists.

What are the symptoms?

There are a total of 57 different ailments which have been linked to the syndrome. The most common symptoms and illnesses cited as Gulf war syndrome include severe fatigue, nausea, fevers, muscle and joint complaints, memory loss, mood swings including severe aggression, insomnia, swollen glands and headaches.

The NGVFA claimed earlier this year that 70% of servicemen who have died since the 1991 conflict killed themselves. The organisation claims these suicides account for 380 out of a total of 537 deaths.

A typical scenario, NGVFA says, is that the stress and illness leads many sufferers to lose their jobs, their relationships deteriorate and they lose their homes and then eventually take their own lives.

The MoD says official statistics record just 97 suicides among Gulf veterans, which is slightly higher than the suicide rate in a similar group of soldiers who did not fight in the war. The NGVFA says some deaths that were recorded as accidental were actually suicides.

How many British service people were in the Gulf?

Around 53,000 British soldiers took part in the Desert Storm campaign, the international effort to liberate Kuwait following the invasion by Saddam Hussein's Iraq.

How many veterans have claims against the government over the illness?

Around 4,000 gulf war veterans have outstanding claims against the MoD for illnesses they believe were caused by their role in the conflict according to Tony Flint, a former chairman of the NGVFA.

Have claimants had any success?

The NGVFA's Mr Rusling won a landmark ruling recently when a war pensions agency tribunal officially recognised Gulf war syndrome as a disease. But many other veterans have been turned down for army pensions because the MoD says there is no such disease.

What evidence was heard at June's hearing?

Statements were made from 14 witnesses including Samantha Thompson, the widow of Gulf war veteran Nigel Thompson who died of motor neuron disease in January, and ex-RAF navigator John Nichol, who was shot down during the Gulf conflict.

Experts also gave evidence on subjects including multiple vaccination, nerve gas, exposure to radioactive uranium and pesticides - all of which have been identified as potential causes of the syndrome.