A report by the U.S. Army Thursday reveals that more than a quarter of U.S. soldiers on their third or fourth tours in Iraq suffer mental health problems.

The survey was based on more than 2,200 soldiers in Iraq and nearly 900 in Afghanistan. Also, more than 400 medical professionals, chaplains, psychiatrists, psychologists and other mental health workers serving with the troops answered the survey.

According to the survey, about 17.9 percent of soldiers in Iraq and Afghanistan had mental health problems in 2007. That is slightly below the 2006 figure of 19.1 percent but relatively consistent with previous years.

However, the problems rise between soldiers returning for a third and fourth combat tour. For example, 27.2 percent on their third and fourth tours suffered mental health problems in 2007. Only 18.5 percent on their second tours and 11.9 percent of those on their first tours suffered mental health problems.

"Soldiers on multiple deployments report low morale, more mental health problems, and more stress-related work problems. Soldiers on their third/fourth deployment are at particular risk of mental health problems,” the report said.

"They do show the effects of a long war," Col. Elspeth Ritchie, psychiatry consultant to Army Surgeon General Lt. Gen. Eric Schoomaker, said of the data, according to the San Francisco Chronicle.

The study also reviewed how much sleep soldiers receive and it found that an average soldier slept about 5.6 hours of sleep per night, “too few to maintain optimal performance.”

The authors of the survey blame the insufficient time at home between deployments for the soldiers’ mental issues.

Soldiers now have only 12 months at home before their next deployment, a period far too short for them to recover. Moreover, the report shows that certain illnesses such as PTSD become more intense as the soldiers prepare to go back into combat.

"One of the conclusions that we draw from this is that soldiers are not resetting entirely before they get back into theater," said Lieutenant Colonel Paul Bliese, the leader of the mental health survey teams.

The report also found that suicide rates “remained elevated.” About 121 Army soldiers committed suicide in 2007, an increase of about 20 percent over the year before.

The report recommended longer time between deployments, more focused suicide-prevention training, and sending civilian psychologists and other mental health professionals to the war-front to add to the uniformed corps there.