Stress and depression are two sides of the same process.

Is depression a disease or condition of the body? Let’s try to figure it out together. Medicine characterizes depression with the following symptoms:
depressed, depressed mood, loss of interest in close, everyday affairs, work;
insomnia, early waking up in the morning or, on the contrary, an excessively long sleep;
irritability and anxiety, fatigue and loss of strength;
lack of appetite and weight loss, or sometimes, on the contrary, overeating and weight gain;
inability to focus and make a decision;
decrease in sexual desire;
a sense of worthlessness and guilt, a sense of hopelessness and helplessness;
frequent bouts of sobbing;
thoughts of suicide.
On the other hand, depression can be seen as a response to stress. We face stress almost constantly, solving one or another problem. For example, a bad mark on an exam or not passing a test causes stress (strong negative emotions) to a greater or lesser degree. We may experience stress while standing in a long line, due to difficulties at work or problems in the family, in the absence of mutual love, when we want to do a lot, and there is no time for that, when there are unrealized opportunities, daily viewing of crime stories on TV and many other reasons which list can be continued almost indefinitely. And after the stress, a reciprocal (protective) reaction of the body necessarily occurs – a state of depression. In response to every single, even the smallest (insignificant) stress, the body responds with adequate depression. But a little stress even beneficial to the body. They constantly train him, bringing him into an activation or training state (in the terminology of the Canadian scientist Hans Selye). The greater the stress, the stronger (deeper) and longer the state of depression. By the time of moderate depression lasts up to two weeks. In severe cases (under severe stress, such as the death of loved ones), depression can last for several months or even several years. That is why the obligatory commemoration of the deceased after 3, 9 and especially 40 days (“parting with the soul”) helps to reduce stress stress first and then get out of the depressive state of family members, relatives and friends. During stress, the body is mobilized and spends most of its energy and directing it to protect the body. After stress, the body is in a state of “discharged battery”, exhaustion, that is, depression, after which a gradual accumulation of energy begins (“recharging” the body) until the moment of full recovery of strength and energy. The process (duration) of depression or inhibition of the body over time (duration) is approximately three times longer than the time of exposure to a stressful situation (the process of arousal of the body) and this must be taken into account when eliminating the effects of any stress, great or small.
And so, the “bombardment” of the body by small stresses and the protection of small and short-term depressions is a normal state of the body, accustomed to permanent protection from the environment. Strong stress, take a lot of energy from the body and cause deep (on the graph, the depth of depression is marked by a segment of the sun) and prolonged depression (severe inhibition of the body with a significant decrease in activity). The body gradually accumulates energy, trying to return to the state of dynamic equilibrium that it had before stress, i.e. self-repairing. I would like to note that the most difficult and dangerous time for the emergence of other diseases for the body during depression does not come immediately after the end of the action of stress (point A, for curve 2), but after some time, from the end of the action of stress (point B ). During this period of time it is necessary to especially monitor your health. It is possible to make an unequivocal conclusion that the cause of any depression (depressive state) is stress. Depression is a non-specific response of the body to stress. Minor depression, with mild stress, is a normal state of the body, with which the body, as a rule, copes on its own. Severe, deep depression, this is a disease and without the help of a doctor here is not enough.
As a rule, in melancholic stress reactions are most often associated with the initiation of a constitution, such as anxiety or fright, phobia or neurotic anxiety. In choleric individuals – a typical stressful reaction – anger. That is why they are more likely to suffer from hypertension, a stomach ulcer.