credible supporting evidence is necessary in order to grant service connection . " Credible supporting evidence " of a noncombat stressor may be obtained from service records or other sources . Moreau v . Brown , 9 Vet . App . 389 ( 1996 ) . This claim for service connection for PTSD is potentially subject to the revision to 38 C . F . R . § 3 . 304 effective July 13 , 2010 . See 38 C . F . R . § 3 . 304 ( f ) ( 3 ) . That revision provides that , in certain circumstances , a veteran who has been diagnosed with PTSD by a VA or VA - contracted psychiatrist or psychologist based on a claimed stressor