An individual is spiritually and physiologically a whole energy
system that interacts with any and all energy systems around it. When
you narrow fields down to the minutia of neurobiology, you eventually
reach cellular energy and physics. Maybe here or beyond is where
understanding and healing begin. One way of thinking about this
is that energies such as chemistries seek the equilibria in which they
comfortably and optimally function, and if out of balance they will try
to regain an equilibrium. There is much to learn, and anyway this is only
unschooled personal opinion.
I see posttraumatic stress as the result of an injury creating an
imbalance that might manifest as out-of-balance behavior.
Here's the rub: it isn't always easy to see that there has been an
injury. If there is a cast on someone's leg, a bone was probably broken,
but if someone is startled and then backs away from something that
may not bother others at all, and that seems odd, the idea of an injury
probably won't be considered. Instead, the behavior would be noticed,
whereas with a cast on a leg, one's thoughts automatically continue past
the cast to the broken leg that it covers. With one, understanding is
automatic, and with the other, it isn't.
Posttraumatic stress isn't easy to see like the cast is. This is often true for both the onlooker and for the injured person. Both can feel completely confused when symptoms occur. However, the imbalance is clear, a change in biology, in neurotransmitters, in chemistries, in intensified reactions and symptoms.