or for aggravation of a pre - existing injury suffered or disease contracted in line of duty . 38 U . S . C . A . § § 1110 , 1131 ( West 2014 ) ; 38 C . F . R . § § 3 . 303 , 3 . 304 ( 2014 ) . Service connection may also be granted for any disease diagnosed after discharge when all the evidence , including that pertinent to service , establishes that the disease was incurred in service . 38 C . F . R . § 3 . 303 ( d ) . Service connection for PTSD requires medical evidence diagnosing the condition in accordance with 38 C . F . R . § 4 . 125