I take it that you refer to Post Traumatic Stress Disorder.
While attached to active duty, military personnel get help from the medical branch of their parent command. It is part of their compensation.
After separation, the Department of Veterans Affairs, (VA) deals with these issues. If PTS is the only condition a vetern suffers, and is Service Connected, (s)he will have lifetime treatment for that condition at VA hospitals and satellite outpatient clinics nationwide.
If there are other conditions that limit the veteran's employability, mobility, or social adjustment, then the VA has specific guidelines for the veteran's limiting condition(s).