Part-time soldiers and their families need more help and support before and after being sent to Iraq, according to a study into the health of reservists.
Reservists fight side by side with regular troops in Iraq
Last year a government-commissioned survey suggested reservists sent to Iraq in 2003 suffered higher levels of mental health problems than regulars.
A follow-up report obtained by the BBC to examine the reasons suggests a lack of support may be partly be to blame.
But some improvements had been made for reservists, said the report's author.
More than 12,000 reservists, including Territorial Army (TA) forces, have been deployed to Iraq in the past four years.
The BBC's Angus Crawford talked to reservist Mike Allen, who came home from Iraq four years ago.
Mr Allen said his marriage broke down and he is still being treated for post-traumatic stress disorder (PTSD).
"I became isolated... I was obviously affected... using booze to try and relax," he said.
He said he was given a 15-minute chat with an army doctor at the end of his tour, and was told to contact the NHS if he had any problems, before being sent home.
However, he said he did not regret signing up.
"If I had the chance I'd continue to serve," he said.
"I don't feel let down by the military, but I feel they could do more."
He was one of those who took part in the biggest study to be conducted into the health of reserve and regular troops who went on Operation Telic - British operations in Iraq - in 2003.
The MoD-funded survey, conducted by researchers at King's College in London, involved about 1,600 reservists and 8,500 regulars.
Some 25% of reservists experienced a mental health disorder, compared with 19% of regular soldiers, it found.
Six per cent reported symptoms of PTSD compared with about half that number among their full-time colleagues.
A follow-up study designed to examine the differences suggests a lack of support for soldiers and families, before and after being called up, may have been partly be to blame.
One of the authors, Professor Simon Wessely of the Kings Centre for Military Health Research, said improvements had been made for serving reservists.
Researchers were now looking into whether this had been matched by similar changes to support for families.
Professor Wessely told BBC Radio 4's PM programme reservists tended to be older and of higher rank than regular troops sent to war zones, and were more likely to be deployed alone.
He said some employers were not as supportive as others and while most families were proud, some spouses and partners were less than sympathetic.
"It's just generally more difficult for you as an individual than if you are part of a large formal unit," he said.
Brigadier David Shaw, who is responsible for much of the day-to-day running of the TA, said areas of weakness had been found but that an "enormous amount has been done" to improve the situation.
The MoD had opened its mental health services to the TA, he said.
It had also increased the numbers of Regimental Operational Support Officers (Rosos) and had twinned TA units with regulars.
"We are so much better at making sure people are prepared for deployment...and we are looking after the TA, we hope, as well as the regulars".
But shadow defence secretary Liam Fox said the government did not understand that the armed forces were "overstretched" and that reservists were not receiving adequate training or preparation.
"Those who do suffer from mental health problems need to have more proactive help... this is a tragic failure," he said.