The search for the common denominator

My search for such a possible denominator began during a rather boring lecture in the field of psychiatry. That day, the psychiatry professor, an inveterate psychoanalyst, lectured on adjustment disorders (a spectrum of symptoms consisting of anxiety, despair, hopelessness, isolation, sadness, and tension in the cervical spine muscles). Generally, this is a pessimistic attitude toward life combined with a lack of interest and joylessness.

The professor listed the symptoms: psychological abnormalities such as anxiety, depression, anger, bitterness, despair, aggression, but also physical symptoms such as tensed muscle. In his opinion, these physical symptomswere purely psychologically induced.Listing the symptoms of this disorder, he mentioned, vivid muscle stretch reflexes (hyperreflexia). These are reflexes that occur when a muscle is tensed and are triggered by the lengthening of a muscle during a rapid movement. An example of this is the knee joint extensor reflex (hamstring reflex) that can be achieved by striking under the kneecap with a reflex hammer, which causes an involuntary extension of the bent leg. The presence of this reflex would mean that the spectrum of symptoms of an adjustment disorder represents a coexistence of purely psychological and neurological symptoms.This made me sit up and take notice. Somewhere in my brain, the alarm bell rang. The question suddenly arose in my mind: what has an organically caused symptom got to do with a purely psychologically caused illness, an adjustment disorder? I realized that there was something wrong with the explanatory model for the development of mental illness. How could a mental illness be half fish (psychological) and half flesh (neurological)? I could not understand that. The convinced neurologist in me at the time knew that the neurological symptoms that can be observed in mental conditions, such as muscle tension and lively reflexes, must also hide an organic cause. The cause of manifestation of these reflexes needs to be sought always in the brain at the level of the so-called upper motor neurons, which connect the brain with the spinal cord.

From that reason, this coexistence of purely psychological and neurological symptoms could not be a coincidence. They could also be found in many other mental illnesses where tension is part of the symptom spectrum.(Urban, 2012), as well as in a mental condition that is widespread today, namely stress. At the time, I reached for my notebook and jotted down 2 mathematical equation:

Legend: The symbol"=" in the first equation denotes the connection to convey a hidden link between a purely psychological and a purely neurological state.

The use of such a"mathematical" form of representation of observed coincidences between phenomena that appear different at first glance entails the risk of being classified as very simplified and dubious by some scientists. This need not always be the case, as the histo