Five Vietnam War veterans, including a New Haven resident, filed a federal lawsuit Monday, claiming that they have been denied benefits and suffered stigma because they received “other than honorable” discharges due to Post-Traumatic Stress Disorder (PTSD). They asked the U.S. District Court in New Haven to designate the suit as a class action on behalf of tens of thousands of Vietnam veterans in the country in similar circumstances. PTSD wasn’t designated a medical condition until 1980, five years after the Vietnam War ended. Many Vietnam veterans with undiagnosed PTSD contend they received other than honorable discharges due to behaviors connected with that illness. Vietnam Veterans of America and its Connecticut State Council, and the New Haven-based National Veterans Council for Legal Redress are also plaintiffs in the suit. They are being represented by the Yale Law School Veterans Legal Services Clinic.