Depression is a complex disease, which affects the physical and mental health of individuals and represents itself in a variety of symptoms and characteristics. Frequently, depression affects the psychological conditions and leads to the reduction of motivation, self-esteem, self-confidence and activities. Among its symptoms, there are anxiety, despair, fear and low mood. Similarly, depression leads to the decline of physical abilities of the organism such as lack of appetite, weight loss, and reduced blood pulse, among others.

Currently, the researches state that both cognitive and biological factors contribute to the occurrence of depression. From this standpoint, it is important to regard the role of biology and physiology in the development and manifestation of depression. Actually, the depression should be treated as a biological disorder rather than the psychological one, since many physiological functions and physical characteristics of the human organism contribute to its development, onset and reoccurrence.

Biological Markers of Depression

It is estimated that millions of people suffer from the depression annually (Reynolds & Johnston, 2013). The frequency of depression occurrence makes it an actual and prominent problem in the modern medicine. At first, it is important to define the causes and factors promoting the development, onset and recurrence of depression in order to appropriately react to it. Biology is one of the most significant aspects, which can cause the development and onset of depression.

To start with, depression can be a result of brain functions and structure. Particularly, the limbic system and activities of neurons can lead to this disease. Talking about limbic system, it is an important unit of the brain, which is responsible for many functions such as emotional control, body temperature, stress response, sleep, appetite, and hormones, among others. It is estimated that any malfunctioning in the limbic system can cause the occurrence of depression. For example, the inappropriate dozes of hormone produced by the hypothalamus or the disturbance in the neurons significantly increase the chances of incidence of depression (Steiger, Dresler, Kluge, & Sch?ssler, 2013). Furthermore, the studies show that the hypothalamus of patients suffering from depression is smaller compared to healthy people. From this standpoint, the biological design and structure of the brain is one of the factors explaining the origin of depression (Steiger et al., 2013).

Moreover, the individual characteristics of the endocrine system and circulation of hormones are other biological reasons contributing to the development and onset of depression (Steiger et al., 2013). The endocrine system performs a number of vital functions such as the generation of hormones, control of the sexual and emotional drives, determination of the body activities (sleep, appetite, brain productivity, etc.) and regulation of organism’s main functions. The abnormal levels of hormones or the irregularity of their production is one of the key elements affecting the emergence of depression. In this case, the disease is the consequence of the biological disorders, which badly influence both the physical and mental activities of individuals (Steiger et al., 2013).

The researches inform about the notable role of cortisol in the incidence of depression. Cortisol is the hormone produced by the adrenal glands situated near the kidneys, which is responsible for the stress response and protection of the organism stability. Thus, the glands continue to produce cortisol even if its amount in the organism excesses the norm, thereby contributing to the development of depression (Morris, Rao, Wang, & Garber, 2014). In fact, the increased level of cortisol in the organism is admitted to be one of the main reasons of clinical depression (Morris et al., 2014). Interestingly, after the decline of depression, the level of cortisol in the body tends to decrease dramatically, confirming its direct influence on the onset of the disease.

Neurotransmitters play an important role in the individual well-being and health. These are chemical substances, which are responsible for interaction between the neurons of the brain. In fact, neurotransmitters send electrical signals and release special chemicals, which satisfy the body’s demand for proper regulation and circulation of the neurons. Thus, depression can occur in case neurotransmitters malfunction and do not send the needed signals in the brain (Sperner-Unterweger, Kohl, & Fuchs, 2014). The problem reduces the interaction between neurons and slows mental processes and activities of the brain. Similarly, it can lead to clinical depression.

Finally, it is important to mention the role of genetics as well as inherited temperament and type of the nerve system in the development and occurrence of depression (Perroud et al., 2013). The experts state that every individual has a congenital type of temperament and character. The type of temperament defines the course of mental processes, reactions and activities of individuals. Some types of temperament and nerve system are more prone to the occurrence of depression compared to the others. For example, melancholic and choleric temperaments are likely to be more vulnerable to the development of depression. From this standpoint, the chances of incidence are greatly dependent on the genes and congenital characteristics of the body (Perroud et al., 2013).

Overall, it is possible to conclude that biology is a prominent factor in the definition of depression and its causes. Many of the physiological functions and structures of the organism can cause this disease or increase the chances of incidence. Therefore, depression is not a purely psychological problem but also a biological one, which presupposes the corresponding treatment and prophylactics.

Alternative Views on Causes of Depression

Though the role of biology in the development of depression is obvious, there are other theories, which connect the disease with cognitive and mental factors. In general, the alternative views argue that biology cannot be the main factor of depression as every organism is individual and unique. Correspondingly, it is impossible to make universal conclusions about the connection between physical disorders and depression, which can be true in all cases. At the same time, cognitive factors of depression are easy to identify and indicate as well as trace their impacts on the occurrence of depression (Weary, Gleicher, & Marsh, 2012). Nevertheless, such theories apply the principle of individuality of every organism and beat a relative character.

To start with, cognitive theories on depression origin state that this disease is a result of emotional and psychological deviations and disorders. The most common reason is the cognitive dissonance, which presupposes the contradiction between personal aspirations and reality as well as cognitive triad concerned with the negative self-esteem and outlook. The researchers argue that depression is a result of the low self-reliance, negative image of the world and reduced self-confidence (Weary, Gleicher, & Marsh, 2012). Apparently, these factors are supposed to cause clinical depression in the majority of cases. However, this theory links depression to cognitive disorders without considering other factors such as living conditions, physical health or social background of patients. Obviously, those factors also contribute to the occurrence of depression and often play a significant role in its development. From this point of view, the cognitive theory provides only a partial explanation of the disease and explains its development, only in some cases. Besides, this theory is more suitable for defining the anxiety, rather than clinical depression (Becker & Kleinman, 2013).

Secondly, cognitive theory suggests that depression occurs in case people do not receive sufficient communication and interaction with other individuals. In other words, this theory connects the emergence of depression with the lack of socialization and relations of patients. Psychologist Albert Bandura states that depression appears when people experience a deficiency of normal communication with other individuals and cannot self-actualize their potential in the society (Mark, Donaldson, & Campbell, 2011). Obviously, this factor should be considered when one discusses the origin of depression. Nevertheless, it cannot be the main reason of the disease as the demand for communication and social relationships is different for various individuals. Correspondingly, it is difficult to measure the appropriateness and sufficiency of social contacts for its diagnosis. Moreover, the depression can occur even if a person has good social contacts, position and reputation. This fact states that depression cannot be viewed as a mere result of lack of socialization. Moreover, this approach does not suggest any relevant treatment and rehabilitation (Mark, Donaldson, & Campbell, 2011).

Thus, cognitive theories of depression origin preserve their actuality only to a certain extent. Moreover, they mostly explain the origin of anxiety, stress, worries or other psychological disorders, rather than clinical depression (Becker, & Kleinman, 2013). However, they cannot substitute the prominence of biology when identifying, diagnosing and treating clinical depression as a complex disease.


The identification of causes of depression requires complex considerations and discussions of both physical and mental nature of the human organism. Some researches connect the occurrence of depression with mental disorders and problems with self-perception, pointing to cognitive factors. In general, these reasons are important when defining this disease, though they cannot pretend to be its major causes.

In fact, depression is the result of biological factors, which operate on the physiological level and determine the development of this disease from the physic point of view. The numerous studies prove that biological, genetic and congenital factors play a significant role in the development of clinical depression. The matter is that biological conditions and functions of the body may be prone to this disease and make different individuals vulnerable to its occurrence and onset.

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