While post-traumatic stress disorder has become a much-discussed affliction, a seemingly more prevalent problem is going largely overlooked: transition stress. Think of it as a clinical-sounding diagnosis for that sense of alienation many veterans feel after they leave the military.

That’s the theory behind Beyond war and PTSD: The crucial role of transition stress in the lives of military veterans, a recent essay by George A. Bonanno, a professor of clinical psychology at Columbia Teachers College, and Meaghan Mobbs, a PhD student at the college and a former Army officer. They contend that though only a relatively small percentage of recent veterans develop PTSD —  somewhere between 11% and 20% for Iraq and Afghanistan War-era veterans in a given year  — the disproportionate attention given to PTSD overshadows a more pervasive problem among vets. (In the essay, Bonanno and Mobbs argue that the rate of PTSD among post-9/11 veterans varies dramatically, with studies “employing methodologically rigorous design elements” reporting rates under 10%.)

“There’s been a tendency to use the treatment of PTSD as a catchall,” Bonanno told Task & Purpose in an interview, citing an anecdote from his time as a therapist at a Veterans Affairs hospital.

“A guy I was treating years ago, I can’t go into specifics, but the problems were really not at all about behavioral symptoms,” Bonanno said. He explained:

The problems were that this man had gone off to war. It was the most exciting experience he had ever had. Then coming back to a small town where he didn’t have as much fulfillment, and life seemed kind of dead to him. And that was really the problem he was struggling with: His life had lost its meaning. It was nothing remotely related to the symptoms you see of PTSD.

Serving in uniform can provide easy answers to heavy questions. A mission brings purpose; your rank and job provide a place in the hierarchy; your squad provides camaraderie; and shared hardship reinforces that bond.

Related: The Suicide Contagion: How The Effort To Combat Veterans’ Suicide May Be Making It Worse »

That easy sense of belonging, Bonanno and Mobbs say, doesn’t exist — at least not in clear-cut terms — when service members leave the military and return to the lives they left years before.

Given that transition stress has gotten so little attention, a quick primer is in order.

What is it?

Transition stress encompasses a number of issues facing transitioning military veterans, which can lead to anxiety, depression, and other behavioral difficulties. They include a loss of purpose and sense of identity, difficulties securing employment, conflicted relationships with family and friends, and other general challenges adapting to post-military life.

Loss of identity may be a root cause.

Transition stress is not as simple as missing the adrenaline-fueled highs of war-time service, though that can be a factor. More commonly, it’s a nostalgic longing for that sense of place and self that many within the military felt, regardless of their MOS or theater of operations.

“For our generation of veterans, for us being an all-volunteer force, we all go in during a period of emerging adulthood,” Mobbs told Task & Purpose. “We’re typically asking ourselves the existential questions: Who am I? What do I want to do? What’s the meaning of life? And the military provides a really ready answer for that. They tell you: You have purpose. What you’re doing is meaningful. You matter.”

The questions don’t stop when you get out, but the answers do.

“[The military] gives you all of these really concrete answers that are very appealing in a variety of ways, and that becomes such a salient part of your identity,” Mobbs said. “And then when you take that all away… how do you reconcile that discrepancy?”

The disconnect between war and “The World” isn’t new territory, of course. In a 2010 article for Vanity Fair, author Sebastian Junger observed that recent veterans “return from wars that are safer than those their fathers and grandfathers fought, and yet far greater numbers of them wind up alienated and depressed. This is true even for people who didn’t experience combat. In other words, the problem doesn’t seem to be trauma on the battlefield so much as re-entry into society.”

We know very little about the prevalence of transition stress, because it hasn’t been studied.

Vets affected by transition stress are “just simply struggling, and they’re struggling with a variety of issues,” Bonanno told Task & Purpose. Though the essay suggested that post-9/11 veterans faced higher levels of stress when they left the military than their forebears, a lack of research into these stressors makes it hard to know for sure if this problem is growing more severe, or if it’s always been there.

“We don’t really know… the extent that it’s new, or a characteristic of GWOT veterans,” Bonanno said.

The civilian-military divide seems to play a role.

Roughly 80% of military recruits have family members who served in uniform; between 22% and 35% have parents who are veterans — depending on which branch you look at, according to Slate. The result is that our all-volunteer military has grown more insular over time, while the majority of everyday Americans have little understanding of what service, wartime or otherwise, looks like.

That gap in experience and exposure, can lead those who have never served in uniform to develop a skewed perspective of those who have, which makes a military transition — already fraught with existential questions — more difficult. Take the still pervasive stereotype of the dangerous PTSD-addled veteran, whether it’s in film, television, or news.

The ‘broken vet’ stereotype is alive and well.

A 2016 survey by Military Times found that roughly 40% of civilians think half of all post-9/11 veterans — that would be roughly 1.4 million Americans — have a mental health disorder.

“Civilians commonly think that veterans are mentally ill,” Bonanno said. “And veterans are very aware that civilians have that perception, so to acknowledge stress and difficulties, you’re kind of saying ‘I’m mentally ill,’ and the only option is to say ‘I have PTSD,’ and that’s highly stigmatized.”

We over-invest in making soldiers, airmen, sailors, and Marines. We under-invest in transitioning veterans.

“We spend millions of dollars and weeks and months indoctrinating and transforming civilians into service members, and they spend their entire enlistment or contract having all those behaviors reinforced, through training, or deployments, or any number of things. And then you transition out,” Mobbs said.

Often, leaving the military involves attending a short transition assistance class that focuses on things like how to write a resume and what to wear to a job interview. “You sit in a classroom for a week and you check a box,” then grab your DD 214, and hit the road, Mobbs said. “By the time you transition out, it’s too late. The horse has already left the barn.”

What to do?

We really need to study these problems before we leap into interventions,” Bonanno said. “Part of what we’d like to see would be a mentor-based approach, with mentors assigned to veterans as they leave the military to just help with the daily things of life and understanding the transition process. Some of the difficult things are just reintegrating with friends and families and managing those relationships.”

UPDATE: This story was updated to clarify that the reported rates of post-traumatic stress among post-9/11 veterans varies dramatically between studies. (1/25/2018; 6:31 pm)

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