(a) Post-traumatic stress disorder suffered by a member of the Texas military forces on state active duty is a compensable injury under this subtitle only if it is based on a diagnosis that:
(1) the disorder is caused by one or more events occurring in the course and scope of the member's state active duty; and
(2) the preponderance of evidence indicates that the event or events were a producing cause of the disorder.
(b) For purposes of this subtitle, the date of injury for post-traumatic stress disorder suffered by a member of the Texas military forces is the date on which the member knew or should have known that the disorder may be related to the member's state active duty.