The VA is in the process of finalizing new rules that liberalize evidentiary standards for proving stressors in claims for PTSD. The goal is to lessen the burden of proving stressors when the basis of the claim is fear of military action and terrorist’s actions. The VA has recently issued a Frequently Ask Questions (FAQ) fact sheet. It is worth reading but it will not answer all your questions. http://www.va.gov/PTSD_QA.pdf
Also this week in a lawsuit brought by a coalition of veterans' service organizations, the U.S. Court of Appeals for the Federal Circuit instructed VA to issue by Sept. 1 a final regulation authorizing payment of claims for AO exposure for ischemic heart disease, Parkinson's disease, or B-cell leukemia for any veteran who stepped foot in Vietnam during the war, or their survivors.
VA has been urging veterans with these diseases to file claims immediately because payments, when they begin, will be retroactive to the filing date. VA lawyers did concede to the court that VA had missed several deadlines set in the Agent Orange Act for reviewing the latest science report and for publishing rules to expand claims eligibility to these diseases.