Depression is a condition characterized by depressed mood and anhedonia. For the depressed, everything seems to have lost value and meaning and life itself does not deserve to be lived anymore, a sense of despair, emptiness, lack of pleasure and motivation prevails in doing the things that previously aroused interest and satisfaction, lack of energy and fatigue. Depressed people often complain about problems related to sleep and appetite, poor concentration, and feel in a whirlpool of negative and repetitive self-evaluating thoughts (rumination): a sort of spiral of negative thoughts is created, aimed at reaching a peak of sadness that, in the long run, becomes a permanent condition. Therefore, the mind is blocked in a whirlwind of recursive and devaluing thoughts from which it is difficult to get out autonomously.
Neuroscience and depression
From a neuropsychological point of view, the areas mainly involved in depression are
the prefrontal areas, the front track, and the limbic system, connected by a series of circuits related to them (Beevers, 2005).
The prefrontal cortex is mainly involved in the execution of superior functions and pulse control. Neuroimaging studies show that there is less glial density in the frontal cortex of depressed people (Havekes & Abel, 2017; Samara et al, 2018). Moreover, the lateral orbitofrontal part is excluded from the mechanism of gratification, thus determining the sense of loss and disappointment experienced by depressed people. This area is also involved in the process of self-perception, in the depressed generates a sense of personal loss and low self-esteem (Disner, Beevers, Haigh, & Beck, 2011).
Moreover, the cortex of the anterior dorsal cingulate gurus is hypo active, while the rostral cortex, on the contrary, is hyperactive. These activation, therefore, would derive from the management of the affective state that a depressed person puts in place in response to the demands of the environmental context (Elliott, Rubinsztein, Sahakian, & Dolan, 2002). The anterior cingulate gurus, in turn, stimulates the frontal lobe to intervene in the further elaboration of the emotional process, but because of hypo activity the emotional state is not solvable and the depressed mood remains (Hamilton, & Gotlib, 2008).
Another system involved in the limbic system, the seat of affectivity and emotions (Redlich et al., 2018). In depressed patients, a dysfunction of the hippocampus is determined in the elaboration of affective responses appropriate to the environmental context, which are often inappropriate. Moreover, the amygdala is involved in the learning and re-enactment of memories with emotional content, so an excessive stimulation by the amygdala of the cortical areas responsible for the processing of memories is the basis of the continuous ruminating of depressed (Keedwell, Andrew, Williams, Brammer, & Phillips, 2005).
An integrated structural and functional model of depression has been identified, according to which a neurological pathology or genetic factors can cause a dysfunction of one or more neuroanatomic components of the circuits involved in the genesis of depression and thus induce a major depressive syndrome (Victor, Furey, Fromm, Öhman, & Drevets, 2010).
In depression, what is not working well, therefore, is the communication and interaction between the prefrontal cortex and the limbic system: the prefrontal cortex, should regulate the emotionality and impulsiveness triggered by the limbic system. Therefore, a reduction of connectivity in the areas involved in the mechanisms of memory formation and re-enactment, such as the medial temporal lobe and the parahippocampal gurus, does not allow the normal performance of functions and from here is generated the reduced ability to concentrate on happy memories and the focus only on sad memories typical of depression (Mayberg, 2003).
Finally, depression would derive from two key processes, the first related to cognitive bias and the second to decreased cognitive control (Disner, Beevers, Haigh, & Beck, 2011). The first reflects a bottom-up process that originates from the hyperactivity of the limbic system that then projects the information to the frontal and prefrontal cortex. As a result, a functional response to amplified emotional stimuli is obtained, which influences the ability to interpret information. The second one would instead derive from a top-down region-specific hypoactivity of the system aimed at inhibiting the excessive activation of the brain areas related to the emotional processing and therefore would allow the persistence of the bottom-up dysfunctional activity (Siegle, Steinhauer, Thase, Stenger, & Carter, 2002).
Neurotransmitters
The onset of depression also depends on the action of a very large number of neurotransmitters, which are generally released from the brain and perform different types of functions (Korb, 2015). When some of these neurotransmitters do not function as they should, some typical symptoms of depression can be observed. In particular, depression is determined by the presence of low levels of noradrenaline, serotonin or dopamine. Therefore, doing so facilitates the resolution of the problem (Redlich, et al., 2018).
One of the most common symptoms of depression is poor sleep quality. Non-restful sleep worsens mood, decreases pain thresholds and interferes with learning and memory processes (Havekes & Abel, 2017). As a result, you are less concentrated, more irritable, and markedly tired. In the brain, lack of sleep has negative repercussions on the prefrontal cortex and hippocampus, and it balances out serotonin, dopamine and noradrenaline levels.
Conclusions
In conclusion, if small changes in life were made, this would result in changes in neurotransmitter activity and positive changes in the neural level, which would result in changes in the electrical activity of the brain. These changes lead to an improvement in the quality of life, i.e. higher serotonin levels.
When the hippocampus recognizes that the context has changed, then it stimulates the prefrontal cortex to find new responses and the circuit, the negative spiral, begins to reverse gear producing, in a chain, a new state of well-being. All this is possible thanks to the help of psychotherapy and, in some cases, drugs.