Traumatic Brain Injuries (TBI) and Post Traumatic Stress Disorder (PTSD) are often used in the same sentence. Most people understand that they are not the same thing, but with the overlapping signs and symptoms, the fact that the prior can lead to the latter, and simply the geography of both injuries (the head), makes them both topics of the same discussions. Both are emerging sciences and there is a lot we do not yet understand about either.

TBI: This is a concussion and can occur outside of combat, but the general concern within the military is from a “blast TBI” or bTBI. This can be quite different from causes of TBIs, as the blast wave does not only smack the head and cause the brain to strike the inside of the skull — it also passes through the head. It can do damage to a good portion of the brain this way. Multiple blasts can result in what’s called chronic traumatic encephalopathy or CTE. A minor bTBI can be recovered from fairly quickly (as far as we know), but a severe one can seriously affect even the most basic brain or motor functions.

TBIs can affect the patient’s mood as well. It’s not that he or she is sad that they were hurt, but the physical traumatic injury has actually injured the brain — the organ that controls emotions. This is where things can get really difficult to distinguish between PTSD.

PTSD: This is also known as PTS; some have changed the name in an effort to steer away from it being perceived as a disorder. Regardless, it is a diagnosable condition that is more than just being sad or nervous all the time. The VA defines it as “a mental health problem that some people develop after experiencing or witnessing a life-threatening event, like combat, a natural disaster, a car accident, or sexual assault.” Many have abused the claim for PTSD for attention and to receive a disability rating, many confuse PTSD with regular anxiety or depression from major life changes, but barring those, PTSD still remains a serious issue for many returning from combat.

To fully understand why the two are often conflated, consider this example:

A soldier is exposed to an IED explosion, suffering a bTBI. During the same incident he sees a friend of his severely wounded — killed even — and he is rushed back to a field hospital. During his treatment he suffers from some typical symptoms of a bTBI: he admits to losing consciousness, his headaches are severe in the following days, and the light (especially at midday) makes him feel nauseous, almost to the point of vomiting. For weeks he has issues finishing his sentences — like he forgot what he was saying halfway through saying it — over and over again.

However, he also just got rattled pretty hard. His friend was killed and that image of his body on the ground, mangled in the dirt — the grotesque distortion of the memory that used to be his friend — that image is seared into his mind and will never leave him. Just thinking about it almost makes him shake — not with anger, not with hate toward the enemy — he just shakes, and he doesn’t know why. He misses his friend, he wishes he was fit enough to return to combat but can’t — these things pass some unknown barrier and go from being stressors to very serious, uncontrollable manifestations within him.

Anyone trying to distinguish one from the other is going to get a lot of blurred lines. His splitting headaches could simply be because he’s more stressed than ever before. His nausea might be a result of PTSD and thinking of the things he saw. More than likely, it is a potent mixture of both.