Mental health services are to improve for British forces reservists, the Ministry of Defence has said.
The health of reserve and regular soldiers was compared
It comes after a report revealed 25% of reservists who had fought in Iraq experienced a mental health disorder, compared with 19% of regular soldiers.
Researchers at Kings College in London said Territorial Army (TA) members had less support than the other soldiers.
But they added that overall, veterans suffered lower levels of illness than their 1991 Gulf War counterparts.
This, they said, suggested there was no "syndrome".
However the team added it was too early to conclude that more symptoms in soldiers would not develop in the future.
Over 10,000 regular and TA soldiers completed a questionnaire asking if they had experienced post-traumatic stress disorder, common mental disorders, general wellbeing, alcohol consumption, physical symptoms or fatigue.
In addition to the difference in common mental disorders, such as anxiety and depression, the survey found TA soldiers had higher rates of post-traumatic stress disorder, fatigue and physical symptoms such as chest pain, shaking bowel problems and sexual performance problems.
Scott Garthley, a former reservist who was injured while serving with 3 Military Intelligence Battalion in Iraq, says he was not given fast enough access to medical help after returning to the UK.
He told BBC News: "According to my spinal surgeon, had I waited for the timeframe that the MoD were working to there was a less than 25% chance that I may walk again.
Lack of support
"As far as psychiatrics are concerned, I developed quite bad post-traumatic stress and that wasn't actually diagnosed and treatment started until 12 to 14 months after the event," he added.
Professor Matthew Hotopf, who led the study, said: "These findings are clearly important, because reservists are being used increasingly in Iraq.
"We think the explanation centres on what happens before and after deployment, rather than while you are out there.
"Reservists feel less prepared, and are not deployed in units in the same way as regulars."
Professor Hotopf added that reserve soldiers may not be getting adequate support, from families and employers or from their regular army colleagues.
In addition, their health is looked after by the NHS, while full-time soldiers are looked after by the Ministry of Defence medical services.
The MoD, which funded the Kings College studies, said that in future, part-time soldiers diagnosed with PTSD or related problems would be offered outpatient treatment by the Defence Medical Services.
Defence Minister Tom Watson said: "My department is carefully considering the recommendation that additional follow-up research is required."
But shadow defence secretary Liam Fox said the report confirms that "the MoD is using reserves as a substitute army, but without adequate training to deal with the sort of enemy action they face in Iraq.
"This raises serious concerns with the levels of care being provided to our reservists who have taken part in operations in Iraq," he said.
'No new syndrome'
A second study by King's College researchers looked at data on the health of 3,642 men who had served in Iraq in 2003 was compared with 4,295 who were in service at that time but who were not deployed.
The researchers found small slight rises in irritability, forgetfulness, feeling distant or cut off, chest pain and night sweats among those who served in Iraq in 2003, compared with peers who did not go.
But the striking differences seen between those who served in the 1991 war and military personnel who were serving then but did not go to the Gulf were not evident, the researchers said.
They suggest the difference may be explained by changes in how immunisations were administered - and an awareness that more interest was being taken in the health of serving personnel.
But Professor Hotopf said that, as PTSD was reported many years after soldiers returned after the 1991 war, longer-term research was warranted.
Charlie Plumridge, of the National Gulf War Veterans and Families Association, welcomed the indication further research was needed.
"The position that the issue warrants continued investigation supports the veterans' claims."
And Professor Malcolm Hooper, who advises veterans' groups, said: "There is a real ill-health problem for some 2003 veterans.
"These papers seek to avoid it and ill-serve the sick veterans returning from this conflict."