related to the Veteran ' s fear of hostile military or terrorist activity and a VA psychiatrist or psychologist confirms that the claimed stressor is adequate to support a diagnosis of PTSD and that the Veteran ' s symptoms are related to the claimed stressor , provided the stressor is consistent with the places , types , and circumstances of the Veteran ' s service , the Veteran ' s lay testimony alone may establish the occurrence of the stressor . When there is an approximate balance of positive and negative evidence regarding any issue material to the determination of a matter , VA shall give the benefit of the doubt to the claimant . 38 U . S . C . A . § 5107 ; see