Introduction Stress

Summary

The driving force of evolution is survival and reproduction, in order to maximize population of the species. The goal is thus not primarily happiness or stabil mental health.
Love, joy, and creativity are products of evolution, but they only fit in because they fulfill the general evolutionary purpose: promote growth.
Stress is a product of early evolution. This tool increased the survival rate by making the individual react to the slightest sign of danger.
This means that we are programmed to be distracted, not to be calm and idle.
People in the western world are far away from the birth place of evolution. Our environment can cause the stress response to be active for much longer than for our ancestors on the savannah. It is this long-term stress that causes the statistics of mental illness to increase drastically.

Human heritage - An explanation to our vulnerability

In order to get a deeper understanding of what stress is and how it affects us, we need to go way back in time. To the time of the evolutionary birth of the brain.

One of the first animals that evolution supplied with a brain was the fish, about half a billion years ago. Pretty soon there arose a part which analyzes threats: the amygdala.
Stress hormone secrete in the body when the amygdala registers a threat which activates muscles, and thereby improve the animal's ability to avoid attacks. Once the threat has disappeared, the production of stress hormones ends.

In general the amygdala only bring benefits to the animal, but during human evolution, human features has evolved that enables the amygdala to become activated more often than what is mentally good for us. When evolution gave our ancestors the ability to remember, then the memory itself of a perceived danger, could activate the amygdala which signals to the adrenal glands(a) to start producing cortisol. Later, the emergence of the speach, enabled our ancestors to tell each other stories about experienced hazards. This caused even non self-perceived events to trigger stress. The amygdala is therefore likely to has caused concern for humans for a long time. Even long before the Buddha for about 2 1/2 thousand years ago.
We can all imagine why the current situation makes us stressed. The amygdala, which initially was an aid to escape from predators by a stress mark that seemed for a minute, has presently become a feature that by some of us is on for much of our day and steal much of our life energy.
Stress generation takes a lot of energy and can during prolonged supplement make the brain malnourished. The brain shrinks. This is a cause of fatigue depression(b).

View the position of the amygdala (shown in red)

(a)Actually, the pituitary gland receiving the signal from the amygdala to secrete the hormone corticotropin. This hormone is transported via the blood to the adrenal glands. The hormone stimulates the adrenal glands to secrete the three main stress hormones: adrenaline, cortisol and norepinephrine into the blood.

(b)Relatively new research shows that impaired memory during fatigue depression is due to a reduced brain, but fatigue is due to an exhausted adrenal glands that no longer has strength to produce enough cortisol to keep blood sugar at a moderate level.
NOTE! Intensive research in this area generates new findings continuously. See the statement above as "facts of today"(2016).

Hippocampus

The hippocampus is the part of the brain that controls memory. The amygdala is closely linked to the hippocampus.
Events that do not cause activity in the amygdala, disappears from the hippocampus and become forgotten. But the events that actually activates the amygdala, causes a reaction in the hippocampus and the event is then saved in the long-term memory. When later the event is recalled again, the amygdala activates as if it were a real threat in the present. The memory arose to increase our opportunities to survive, but sometimes it can seem the opposite.

Isolation leads to depression

Apart from the risk of being killed by a predator, our ancesters were exposed to great danger if they were expelled from their group /tribe. To be alone on the savannah was a life threatening situation.
That's why the brain is programmed to reward us with oxytocin, the feeling-good-hormone, if we are among a group of people in which we feel safe. But if we feel lonely, the brain will initiate for stress hormones to be pumping out in our bloodstream.
This is why our vulnerability regarding loneliness, is another factor that can cause depression.
Research shows that people who live in cities have a much higher stress supplement than people living in rural areas. The hypothesis is that people living in the country has a greater need for cooperation and thus has a larger network than people in cities. The majority of people in the cities do not even know their neighbors ... The following link shows that the probability of an early death is 45% higher for those who are alone. As a comparison, the same figure for overconsumption of alcohol is 30% and for obesity 20%. (See movie...)

"Everything that keeps you away from your true self, causes stress."

Hierarchy contributes to depression

Early humans were hunters-gatherers.
In these societies all food was divided equally among group members.
The reason for this egalitarian society was that the pursuit of food demanded cooperation, and the motivation for cooperation was to get part of the prey.
When Western psychologists does research among the few remaining communities of hunter-gatherers of the world today (so called indigenous people), they find extremely few (if any) with the diagnosis: depression.
When humans later on settled and began to cultivate the land, a hierarchy arose, where some people gained more power than others.
This is our society, and currently it has several hundred million people that suffer from depression.
There is a greater risk of depression in work situations where the individual worker is controlled by a hierarchical order, and thus is unable to influence the work situation.
It can appear strange that a predator like the human, isn't controlled by similar hierarchic structures, like other groups of predators in nature. Modern science suggests, however, that hierarchy is detrimental for human cooperation, and that our large brain is a result of a human evolutionary success story of cooperation and not intellectual thinking.

The Hadza tribe in Tanzania, often constitutes a representative group of hunters-gatherers in scientific studies. This tribe shows an average 'depression index' four times lower than the average healthy Japanese. Consequently, the Hadza tribe has received and attracted attention in several books, and the society has been studied by peace and conflict researchers who seek functions to reduce risk of conflict in our society.

Unfortunately, these cultures are at risk of extinction when modern cultures continuously "pushes" these indigenous people aside, in order to meet their own interests. Read about the bitter truth for the Hadza people in the following article: washington post.