Forty years after the end Vietnam War, troops who served there continue to struggle with post-traumatic stress, according to a study published in the September issue of JAMA Psychiatry.

The National Vietnam Veterans Longitudinal Study concludes that 271,000 Vietnam War veterans suffer from varying levels of post-traumatic stress, and that one-third of that number have a major depressive disorder 40 years after the war.

“An important minority of Vietnam veterans are symptomatic after four decades, with more than twice as many deteriorating as improving,” reads the report. If left untreated, symptoms of post-traumatic stress can be exacerbated as individuals grow older, especially when combined with substance abuse and co-existing psychiatric disorders.

“Policy implications include the need for greater access to evidence-based mental health services,” the report recommends, citing the stressors of aging, retirement, chronic illness, declining social support and the recurrence of unwanted memories as contributing factors to lifetime post-traumatic stress disorder among veterans.

After post-traumatic stress disorder was included in the Diagnostic and Statistical Manual of Mental Disorders in 1980, studies showed a gradual decline in post-traumatic stress rates among Vietnam veterans and a diminished effect during a 10-year follow up. However, concerns persisted that combat and wartime stressors were likely to continue having an impact in patients’ lives.

The study — which was led by Dr. Charles R. Marmar of the New York University Langone Medical Center — was published online in July and designed to reassess veterans who participated in the original National Vietnam Veterans Readjustment Study that was conducted from 1984 through 1988. The new data appears to show that the effects of post-traumatic stress have a longer lifespan than initially thought.

Recommended

In The Military? Tips For Saving Money At Every Stage

Think Your Absentee Ballot Doesn’t Matter? Here’s Proof It Does

9 Ways To MacGyver Your Life With A Rip It Can

10 Essential Fieldcraft Survival Tips, According To A Veteran

How This Soldier Used His Military Skills To Build A Career And Serve Veterans At Sodexo

With the wars in Iraq and Afghanistan drawing national attention to wartime post-traumatic stress, the implications of the report are of particular note for veterans of America’s most recent conflicts. More than 2.4 million service members deployed to either theater at least once, and according to the National Center for PTSD, between 11 and 20% of Iraq or Afghanistan veterans will have post-traumatic stress in a given year.

The survey was administered to a representative national sample of 2,348 veterans who served in the Vietnam theater of operations. It consisted of a computer-assisted telephone survey, a clinical interview, and a self-reported questionnaire, administered between July 2012 and May 2013.

These findings raise questions about the necessity for mental health care services, both now and in the future, and underscore the need for continued care for veterans with post-traumatic stress disorder.