. R . § 3 . 304 ( f ) ( 3 ) to liberalize the evidentiary standard for establishing the required in - service stressor in certain cases . The current , liberalized version of § 3 . 304 ( f ) ( 3 ) states that when the claimed in - service stressor is related to the veteran ' s " fear of hostile military or terrorist activity , " the following shall be demonstrated to establish service connection for PTSD : 1 ) the claimed stressor is consistent with the places , types and circumstances of the veteran ' s service ; 2 ) a VA psychiatrist or psychologist , or contract equivalent , confirms the claimed stressor is adequate to support a diagnosis of