Middle-rung officers as compared to jawans and junior commissioned officers were more vulnerable to stress in the armed forces, according to a study conducted by a psychological research institute.

"Uncertain environment and domestic stresses are responsible for most of the psychological problems in various groups of the armed forces engaged in anti-terrorism operations," Defence minister A K Antony told Rajya Sabha during Question Hour quoting from the report.

He said the Defence Institute of Psychological Research had conducted two studies on the psycho-social aspect of optimising the operation efficiency of security forces to combat insurgency in the five years from September 2000 to May 2005.

Antony said mental disorders in the form of post-traumatic stress disorder had also been observed, which formed the basis of various symptoms. He said another study was carried out in December 2006 on suicides and fratricides among troops deployed in counter-insurgency and some of the suggestions thrown up were a liberalised leave policy and deployment of psychological counsellors.