To him, traumatic brain injury means more than the short-term memory problems that make him put tracking devices on his keys, phone and other everyday items so he can find them again.
TBI, which is often closely linked with post-traumatic stress disorder, also contributed to an "existential crisis" that almost took Smith's life in 2016.
"When you live a life of service, purpose and mission and your personal self-identity is defined and provided to you by your job and that's taken away, that really causes an existential crisis with any individual," he said.
Compounding those "demons of the past -- the things that you haven't really worked through or processed yet," brought him to a breaking point in January 2016, he said.
Smith recalled that he sat on the couch and put his gun in his mouth, but he passed out before he was able to pull the trigger. When he came to, his then-fiancee -- now his wife -- was there.
"You get really good at hiding that [pain] from the world," he said, "and we get really good at hiding it to the point where we can even hide it from those that we love."
Traumatic brain injury made headlines recently when President Donald Trump referred to injuries sustained by troops after a Jan. 8 Iranian airstrike as "headaches."
"I heard they had headaches and a couple of other things ... and I can report it is not very serious," Trump said at a press conference in Davos, Switzerland, according to an AP report on Jan. 22. "No, I don't consider them very serious injuries relative to other injuries that I've seen. I've seen what Iran has done with their roadside bombs to our troops. I've seen people with no legs and with no arms. I've seen people that were horribly, horribly injured in that area, that war."
His comments have drawn sharp criticism, especially as the number of troops diagnosed with TBI after the attack continues to rise. On Jan. 30, officials raised that number to 64, with the possibility of more to come.
The issue has drawn attention to what is considered the "signature wound" of the post-9/11 war. More than 410,000 service members have been diagnosed with TBI since 2000, according to the Defense and Veterans Brain Injury Center (DVBIC). This is in part due to the prevalence of enemy fighters in Iraq and Afghanistan using improvised explosive devices.
But doctors are still working out how to make tests sensitive enough to show mild TBI and determine who will need a longer recovery. Physicians also have yet to agree on the level of activity a patient should engage in after a TBI.
No matter the case, to Dr. Brent Masel, director of the Brain Injury of America Association, TBI is by no means a minor injury.
"[Trump's] just wrong," Masel said.
TBI diagnoses are broken into three types: mild, moderate and severe. Those classifications refer to the patient's status of consciousness after the event.
Mild TBIs are most often called a concussion. That's when a person is awake after the event. They're usually dazed -- seeing "stars" or "spots" -- and confused.
Dr. David Cifu, a Virginia Commonwealth University Health professor researching TBI for the government, said people look pretty good in this state so it's easy to miss that the patient has 10% less ability in their hand movements, or they're off balance.
With a moderate TBI, the person may be unconscious for up to 30 minutes. Severe TBI results in a coma.
Dr. Jamshid Ghajar, president of the Brain Trauma Foundation, said the classifications serve two purposes: "One is to recognize the impairment and, two, it's correctable," he said. "You can actually treat it."
In the long term, TBI patients can experience temporary gaps in memory, irritability, depression, anxiety and trouble sleeping, among other issues, according to the DVBIC, which calls it a "significant health issue."
Alex Balbir, from the largest nonprofit organization helping veterans and active-duty service members, the Wounded Warrior Project, pointed out TBI's cognitive deficits.
"Your supervisors, your commanding officers, might look at you and say, 'You know what, I'm not quite sure what's happening to you right now," Balbir said, adding they would see a lack of focus or confusion. "You find yourself breaking those routines, breaking those molds that you developed over the years, and it changes your persona just a little bit."
The Evolution of TBI Treatment
The days of sitting in a dark room until the patient's headache goes away or waking him or her every so often are mostly in the past. However, doctors still differ on what exactly should be done in the days following a TBI.
"A lot of physicians will say, 'Well, you shouldn't do anything. Go into a dark room, don't strain the brain and wait until you recover,'" said Ghajar, who is also the director of Stanford University's Brain Performance Center. "And we have a national epidemic of people that are sitting in a room waiting for their headache to go away.
"Well, we and others have published literature that found that early exercise after a concussion speeds recovery," he continued. "So this idea of 'don't strain the brain' is not a good one because you're actually isolating people and causing a delay in their recovery."
Ghajar said he introduces therapy like one would do with any injury. The patient might have issues with their eyes not focusing or their neck hurting, so they would be connected with a specialist.
He said it's best to identify the patient's symptoms and introduce therapy early, even though it may provoke TBI symptoms like headaches.
"The brain is a prediction machine and, when you get a concussion, that's what goes -- prediction," he said. "What happens is, you're unable to predict well and so, when things are moving in the outside world, you're unable to tell where they're going to be or where you're going to be, and that causes error signals in the brain, which produces headaches, dizziness, fogginess, feeling out of sync."
For Cifu, TBI treatment is about helping the whole person. While the vast majority of patients will be fine after two weeks, those with chronic conditions such as anxiety, sleep apnea or a history of migraines often take longer to heal.
For example, if the patient is suffering from anxiety, Cifu said he might refer them to a psychologist, in addition to the therapy Ghajar mentioned.
The Wounded Warrior Project is investing in a similar holistic treatment strategy for veterans suffering from TBI.
"I don't like to call it a 'multidisciplinary approach' because that means that the patient is going from one person to the next person without them talking. What we hope to have is more of an interdisciplinary approach," Balbir said.
The WWP's "secret sauce," he said, is forming a cohort of veterans to go through treatment together. This creates a support system for veterans during the program and post-treatment, where they can check on each other.
Treatments at civilian facilities are similar to the Pentagon's, requiring eye and neck therapy as appropriate to treat the symptoms.
Former DVBIC director Kathy Lee noted that TBI does not just affect troops who have seen combat. Some 80 to 85% of TBI events tracked by the Defense Department happen at bases stateside, often as a result of traffic or training accidents.
In 2018, the DoD added eye tracking to its Military Acute Concussion Evaluation 2, or MACE 2. Four years earlier, officials established a six-step program to introduce service members back to physical activities gradually. Today, officials are working to include TBI instructions into the DoD guidance on brain health.
Lee, who is now special assistant to the assistant secretary of defense for Health Readiness Policy & Oversight, said education remains a significant problem, because many people with TBI do not recognize its symptoms.
"It's very rare that a person says they're having 'attention problems,'" she said.
That's one reason why the DoD has instituted mandatory TBI assessments for troops who experience a potentially concussive event. This also eliminates the "stigma" associated with getting treatment.
After a diagnosis of mild TBI, a service member will receive a "Return to Activity" educational brochure to track their symptoms and explain the stages of light activity they must go through before returning to duty.
The Department of Veterans Affairs created a concussion screening procedure in 2007 for all Iraq and Afghanistan veterans when they come in for care.
The VA does not list all its TBI treatment methods on its website, but says that "treatment typically includes a mix of cognitive, physical, speech, and occupational therapy, along with medication to control specific symptoms such as headaches or anxiety."
The Future of Treating TBI
Military care providers are eager to find an objective test that will help diagnose TBI without relying on accounts of patients' self-reported symptoms.
Last year, the Defense Department and the VA announced a joint grant for TBI research with each giving up to $25 million for five years to look at the least-studied TBI category: concussions.
Cifu's team, which received the grant, is researching a way to better diagnose mild TBI. The current best practice is simply talking to the patient.
Researchers are looking into "biomarkers" in the blood and brain that might reveal the presence of a mild TBI; current scans are not sensitive enough to show the damage.
Cifu said his study is looking into whether it might be better to use multiple tests, instead of just one, to reach a diagnosis. Other research areas might lead to early detection of which patients will take longer to heal, he said.
Meanwhile, VA researchers are looking into methods such as magnetic brain stimulation and protein injections to treat symptoms of headaches, anxiety and mood swings.
"The treatment involves taking an electromagnet [a wire wrapped around a solid coil], charging it with electricity, and applying it to specific points on the skull to target the underlying brain area," the VA said on its website. "The result is a powerful magnetic field that can affect brain cells."
Smith, the Green Beret, said he has since discovered his purpose outside of the military by educating the public on TBI and helping active-duty members and veterans cope with its effects.
TBIs are not visible to the public like the loss of a limb, he said, so it's important to really push the question of "Are you OK?" to someone suffering from it.
Since it's part of the military's culture to carry your own weight and not be a burden, he continued, a veteran will avoid saying something so they're not labeled as complaining or boasting.
"That person is never going to look at you and say, 'I need help,'" Smith said. "That person is never going to say, 'I'm drowning.'"
-- Dorothy Mills-Gregg can be reached at firstname.lastname@example.org. Follow her on Twitter at @DMillsGregg.