Our conception of the human “mind” is a manifestation of brain function. In turn, the brain is composed of numerous autonomous, but highly coordinated functional units.
If one information processing unit malfunctions or slows down the effect will cascade, compromising the functioning of all others connected regions that rely on it. Some have analogized this to an airplane factory with its multiple coordinated assembly lines. Smaller problems in one line may go wholly unnoticed, yet the manufacturing defects introduced eventually lead to a critical component failing, ultimately compromising the whole aircraft.
It is poorly understood what causes the mental disintegration we term psychosis, but it appears to be evenly attributable to genetic predisposition and environmental triggers (aka the Stress-Vulnerability Model.) Going back to the airplane analogy, imagine if the bolts that secure the wings to the fuselage were not manufactured to specification. The plane would initially fly normally, but when confronted by a heavy storm, the accompanying strong winds would put such a strain on the defective bolts that they give way with catastrophic consequences. That “stress” plays such an important role in the development of psychosis it should be no surprise that two of the best described risk factors are physical trauma and psychological trauma – Sgt. Wall suffered both.
When the mind begins to shatter (psychosis) it does so incompletely, insidiously without detection. What people often term a psychotic break is not a sudden event like a heart attack, but rather the end stage of progressively deteriorating brain function. The period leading up to the point of florid psychosis, where schizophrenia can be diagnosed, is termed the “psychotic prodrome” and can be years long. Because the symptoms onset gradually, the patients, families and close friends will often unconsciously overlook symptoms, or seek to rationalize them.
When the break from reality occurs, it does so incompletely, a few florid delusions intermingled with amidst logic and sanity. This situation was wonderfully described in a 19th century horror story by Guy de Maupassant that reads:
“I have seen mad people, and I have known some who were quite intelligent, lucid, even clear-sighted in every concern of life, except on one point. They could speak clearly, readily, profoundly on everything; till their thoughts were caught in the breakers of their delusions and went to pieces there, were dispersed and swamped in that furious and terrible sea of fogs and squalls which is called MADNESS.”
This compartmentalization of their insanity is the norm early in the illness and allows these delusional beliefs or misperceptions to easily remain hidden and not appreciated by those around them. In other words, simple, everyday conversations will not uncover the growing psychosis, until very late in the illness.
Psychosis (aka positive symptom psychosis) is a symptom of mental dysfunction that can be broken down into three domains: distorted thought process, faulty sensory perception (hallucinations, illusions), unusual thought content (delusions) AND little to no insight.
How does this all fit together?
For example, it is common for patients with schizophrenia to hear voices of people who are not there (auditory hallucination), and “see” people lurking in the shadows (visual illusion), always just out of view. It is easy to so how these processes once started can snowball, what started out as suspiciousness turns to full paranoia where your enemies are everywhere, and eventually you may believe that these enemies have even replaced the people you trust. At this point fear and helplessness can overwhelm what little capacity for logical thought remains intact, and from there, impulsive aggression.