The U.S. Army's surgeon general has declared on Thursday that a new survey reveals 30 percent of troops have developed mental health problems due to stress.

The survey was carried out on 1,000 troops stationed overseas, in Iraq.

The study found that many have developed stress-related symptoms like anxiety, depression, nightmares, anger and an inability to concentrate. Some troops have even developed a serious mental illness like post-traumatic stress disorder (PTSD).

On the contrary, Col. Elspeth Ritchie, a military psychiatrist, reveals that 3 percent to 5 percent soldiers were diagnosed with a significant mental health issues immediately after they leave Iraq.

The survey has also been carried out on the troops who were in the combat zone in 2004. Only 13 percent developed mental health problems, the study shows.

Lt. Gen. Kevin Kiley has ascribed the mental disorder of the 30 percent of troops to the post-combat stress problems. According to him, the symptoms generally take time to develop once the danger is over.

However, military medical officials have urged not to take the survey findings in a negative spirit towards warfare. They term anxiety and stress as normal reactions to warfare.