Thousands of British troops who fought in Iraq are to undergo screening in the biggest-ever study of the physical and psychological impact of going to war.

The landmark research will give early warning of any repeat of the mysterious illnesses suffered by soldiers following the 1991 conflict.

But it will go much further in providing the first detailed picture of the human cost of modern combat for both the troops and their families.

Early studies have already suggested one emerging cause of trauma could be concern over 'friendly fire' incidents, with at least five British personnel accidentally killed by American forces in Iraq.

But the research, funded by the Ministry of Defence and carried out by a specialist unit at King's College, will cover possible triggers for illness, from controversial vaccinations given to protect against germ warfare to the effects of depleted uranium used in allied weapons and stress factors related to individual soldiers' experiences.

'The immediate concerns are first, whether or not there will be a repeat of the kind of physical health problems experienced by Gulf One soldiers and, second, the increasing concerns about psychological issues, including post-traumatic stress,' said Professor Simon Wessely, who will lead the study.

'They expect the Iraqis to shoot. They're the other side. But there is something very, very psychologically disturbing about being shot by your own side,' he added.

Troops who served in Afghanistan, Sierra Leone and the former Yugoslavia as well as Iraq will be among the 16,000 tracked over a decade to establish the long-term impact on health and well-being. Their families will also be monitored to assess the impact on relationships with spouses and children.

Exhaustive medical research has produced no evidence of a recognisable Gulf War syndrome. But Wessely said it was clear that service in the Gulf had a particular effect on servicemen not experienced by those deployed elsewhere, for reasons that remain unclear.

Many sick veterans blame a cocktail of vaccines and tablets to protect troops from chemical warfare given before the 1991 deployment: the Gulf War Veterans Association says it is already in touch with 25 service personnel who fell ill after being deployed to Iraq last year, despite changes to immunisations.

Shaun Rusling of the Veterans Association said veterans had little confidence in MoD-funded studies. 'Blood samples should have been taken from soldiers prior to vaccination and then again after it this time,' he said.