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How Do Genetic and Environmental Factors Contribute To The Expression of Depression? Research Paper


Depression affects very many individuals in the world and results in reduced productivity in the workplace. Depressed individuals experience feelings of hopelessness and helplessness which makes them have negative perceptions about their immediate environment and some even develop suicidal thoughts.

This paper will look at the link between genetic factors and the environment on expression of depression. Some research studies that have been carried out have shown that some individuals might be predisposed to depression more than others. Such individuals might have body systems that either produces excess stress hormones or neurotransmitters that are not as balanced as they should.

The result is that an individual’s mood is affected which might affect their work and relationship with their family and friends. People who are predisposed to depression should avoid excessively stressful situations to avoid imbalance of the endocrine or nervous system. The paper will also look at methods, results and recommend areas that can be further researched on concerning the area of depression.


Depression is a clinical condition that affects the way an individual thinks or acts. Depression has been mentioned to result to sadness, feelings of stress and hopelessness about situations in an individual’s life. Depression affects physical functioning, thoughts, mood, behavior and communication.

Often, depression is mistaken with sadness but it should be noted that sadness usually goes on for too long. Depression usually results in a change in an individual’s life in a negative manner. Depression does not dictate on gender, age or race. Depression affects about 9.5% of adults in the United States of America (Ebert & Ebmeier, 1998 p. 112).

Majority of people who suffer from depression are reported to being suicidal. Depression affects the way that the affected individuals deal with those that are close to them.

Most clinically depressed individuals usually withdraw from close relationships that they might be involved in and at the same time, such individuals develop poor eating habits and they might even stop taking care of themselves in terms of physical appearance, health and work.

Unfortunately, no laboratory tests can be carried out to determine whether an individual is clinically depressed. Most doctors usually try and carry out other medical tests that could relate the condition of the individuals to their clinical depression (Lambert & Kinsley, 2011 p. 41).

Clinical depression can usually be related to the physical conditions that result such as sudden weight loss or weight gain, frequent headaches, indigestion, stomachaches and other physical symptoms that might prove difficult to treat because they would fail to respond to treatment.

Emotional manifestations of depression include feeling hopeless, anxious and/or agitated. People with depression have also been quoted to have suicidal thoughts. Such thoughts can be associated to clinically depressed individuals feeling helpless about their life and things that they might be going through in their lives (Hays, Wells & Sherbourne, 1995 p. 31).

Friends and family members of individuals who experience depression might cite that the depressed persons change in the way that they take care of their personal looks or health. Depressed people can stop taking care of themselves because most of the time they feel agitated and they might feel that taking care of their health or personal appearance would not result to anything meaningful.

A common symptom of depression is forgetting one’s responsibilities. For example, a severely depressed person might forget that they were supposed to pick up their child from school or fail to take care of their duties in the home or at work and fail to have a credible explanation.

Depression can manifest at various levels with minor forms of depression resulting into major depression if symptoms are not treated on time (Monteleone, 2001 p. 67).

Major depression can occur at one or two times in a person’s lifetime characterized by heavy feelings of agitation, hopelessness and anxiety. The symptoms of depression can interfere with an individual’s ability to perform their duties.

Such depression has been found to be triggered by certain negative life-changing events in a person’s life such as the death of a loved one, a life changing accident such as a fire resulting in change in physical appearance or loss of life savings for example after being conned by a professional con artist (Bradshow & Mattingley, 1995 p. 19).

Dysthymia is another form of depression which is less serious in comparison to major depression. Dysthymia usually manifests itself over long term periods impairing an individual’s ability to attend to their duties and fulfilling their responsibilities.

Clinical depression can also manifest itself as manic depression whereby an individual might experience alternating periods of feeling hopeless and helpless to feeling very active and full of life (Cutter, Norbury & Murphy, 2003 p. 32).

Statement of Question

How do genetic and environmental factors interact and contribute to the expression of depression? Depression affects approximately 19 million people in the United States and many more all over the world. The exact causes of depression are not known which makes the treatment of the condition much more difficult.

Some individuals seem to be more predisposed to depression in comparison to others. It is important to find out the cause of depression so that the condition can be effectively treated and also in good time.

There are many people who commit suicide due to the high depression levels that they experience. Understanding of genetic and environmental relationship of depression can result to prevention of ‘trigger factors’ that result in depression (Cutter, Norbury & Murphy, 2003 p. 98).

Description of Neurochemistry or Functional Neuroanatomy

Neurochemistry of depression has been explained using various neurotransmitters, neurons and hormones in the body. Neurons are structures found in the nervous system that are responsible for passing of messages across the body.

Neurotransmitters in the body are responsible for the transmission of impulses in the nervous system, a very important functional part that of the body. Norepinephrine, serotonin and dopamine are three of the most important neurotransmitters in the body whose levels are found to be abnormal in people that suffer from depression.

The three neurotransmitters are responsible for many bodily, psychological and emotional functions in the body (Sheline, Gado & Kraemer, 2003 p. 69).

Sleep, food appetite, sexuality and moods are some of the body functions that are affected by levels of neurotransmitters in the body.

Research studies that have been conducted over time on levels of the three specific neurotransmitters; dopamine, serotonin and norepinephrine, have been inconclusive about their direct relation to the increased levels in feelings of hopelessness and helplessness which can sometimes be as serious as being suicidal.

One of the reasons that make the study of the stated neurotransmitters difficult is that they are released in minimal amounts and the amounts are then used up in their respective functions. The neurotransmitters are released in the brain which makes their extraction difficult because the brain is very sensitive (Hays, Wells & Sherbourne, 1995 p. 111).

The action of the neurotransmitters is very fast, making it difficult to measure the specific levels that are released and the resultant effects after their release. However, the metabolites do not give clear and sufficient information on ways through which neurotransmitters level in the body lead to depression.

If scientists could be able to measure the amount of transmitters that are released at different times when individuals have different experiences in their lives, it would make the process of measuring the neurotransmitter levels much easier (Bradshow & Mattingley, 1995 p. 96).

It is believed that people’s reactions to stress that they encounter in life is one of the factors that leads to changes in the levels of the chemicals that are involved in bodily changes such as the amount of neurotransmitters that are produced in the body.

It is not clearly known whether it is the stress that people encounter that leads to changes in the levels of neurotransmitters or whether it is the level and the changes in neurotransmitters that lead to changes in stress levels in people (Hays, Wells & Sherbourne, 1995 p. 65).

The endocrine system also offers possible explanations into depression among people. The endocrine system is composed of different glands that are responsible for production of very important hormones in the body. Hormones contribute to the initiation and regulation of different hormones in the body.

Hormone levels are regulated by the level of the ongoing processes in the body. A carefully controlled feedback system ensures that hormonal levels are always kept constant in the human body.

The hypothalamus which is located in the brain is responsible for release of some of the hormones that are transported to the pituitary gland which is responsible for the release of other hormones in the body. The hypothalamus is responsible for a sequence of events in the endocrine system that leads to the release of the stress hormone cortisol.

The hypothalamus produces corticotrophic releasing hormone (CRH) which in turn stimulates the pituitary gland to release adrenocorticotrophic hormone (ACTH). The ACTH is transported to the adrenal glands which secretes and releases cortisol hormone into the blood (Gelder, Mayou, & Geddes, 2005 p. 108). This process occurs when cortisol levels in the blood are low.

When cortisol levels are high, the hypothalamus is signaled to stop the production of CRH which is the initial hormone in the production of cortisol hormone. Normal production of cortisol hormone also involves the release of the cortisol between 8.00 a.m. and 4.00 p.m.

Individuals who are depressed might be found to have a faulty production time where the cortisol is produced at night or it might be produced throughout the day and night and at high levels regardless of the cortisol levels that might already be in the blood (Gelder, Mayou, & Geddes, 2005 p. 48).

Although there is no confirmation test for an accurate diagnosis of depression, the test can offer an insight into an existing stress condition whereby other tests should be used to confirm depression in an individual. The dexamethasone is usually administered before sleeping at night to individual who are being tested for stress and their cortisol levels are checked in the morning and again in the evening.

The diagnosis for depression is made using the medical logic that the endocrine system senses that the cortisol levels in the body are sufficient and therefore no more cortisol is produced.

For individuals with clinical depression, cortisol hormone continues to be produced therefore when tested, cortisol levels in the blood are quite high and the production levels are not affected by the administered dexamethasone (Gelder, Mayou, & Geddes, 2005 p. 75).


Data for the relationship between genetic factor and environmental influence that might affect depression was sourced from existing literature from peer reviewed journals and published texts on the topic (Gravetter & Wallnau, 2008 p. 23).

Results/ Discussion

Research findings from studies carried out on the relationship between environmental and genetic factors indicate that some individuals might have a variation from the normal allele responsible for serotonin-transporter linked promoter region (5-HTTLPR).

The studies concluded that the deviation from normal structure for the allele could be a major contributory factor to the predisposition of some individuals to depression. When subjected to the same kinds of environmental stress levels, certain individuals seem to cope better while others might get severely depressed.

This genetic aspect of neurotransmitter related genes could offer a viable explanation to the cause of depression among different people in the world (Monteleone, 2011 p.1)

Genetic factors are some of the aspects that determine the size of different organs in the body. In relation to this factor, a study was conducted involving depressed patients and controls. It was found that some of the depressed patients had a larger volume of the adrenal gland and of the lateral ventricles.

Different parts of the brain were also found to have different sizes than normal in patients that had been diagnosed with depression. Smaller sizes of hippocampus, thalamus, basal ganglia and frontal lobe were observed in patients who had been diagnosed with depression.

Therefore when subjected to stress environment factors such as loss of a loved one, job loss, medication that might interfere with neurotransmitter levels as a side effect and many other stressful events, such individuals with genetic predisposition might suffer high levels and rates of depression (Monetleone, 2011 p. 2).

All individuals have body systems in place that are supposed to help them cope with stress such as increased cortisol level which might signal a reduction in the production of cortisol by the pituitary gland. Pressure at work, planning for a project, divorce and reading for exams are some of the life events that have been associated with depression in some individuals.

There are many individuals who are able to deal with these kinds of environmental stressors properly but some other individuals especially those that have genetic predisposition factors might not be able to handle the environmental stress factors well. Such people might already have body systems that lead to overproduction of neurotransmitters and hormones that lead to depression.

Women have also been observed to be more prone to depression compared to their male counterparts. One of the reasons could be the high levels of estrogen that women produce compared to men (Fournier et al, 2010 p. 52).

In most cases of clinical depression, patients are usually treated using prescription drugs that work to affect the three neurotransmitters that are related to depression. Such compounds include; SSRI (Selective Serotonin Reuptake Inhibitors) and SNRI (Serotonin- norepinephrine reuptake inhibitor).

These compounds work to return the normal levels of the neurotransmitters. Cyambita, Lexapro and Zoloft are some of the prescription drugs that contain the neurotransmitter compounds. However, the drugs work best when they are used alongside counseling by a qualified professional psychiatrist (Fournier et al, 2010 p. 50).

Limitations and suggested future research

Depression leads to feelings of hopelessness and one of the consequences of such feelings for patients is that they might not want to seek treatment. This limits the number of individuals who can provide the necessary data for better study and solution to the problem of depression.

Depression patients refusing treatment would also limit the number of cases that are available for study of the relationship between environmental factors and genetics in the depression patients.

Future research should be carried out to determine the cause in the defect of the allele that seems to make some individuals more prone to depression than others. Research into therapeutic measures that can be taken to repair the damage done on the alleles related to genetic predisposition should also be looked into.

The scientific methods to be used can include gene therapy or other biochemically and biotechnologically innovative methods (Hays, Wells & Sherbourne, 1995 p. 78).


The paper has looked at the interaction between genetic and environmental factors that lead to depression in general. The paper has first given a detailed description of the neurochemistry behind depression and the symptoms that are associated with the condition.

Depression is associated with an imbalance of the neurotransmitters serotonin, dopamine and norepinephrine. A hormonal imbalance such as excess production of cortisol has also been linked to the manifestation of depression in individuals.

One of the reasons proposed as leading to depression among individuals is the variation of the genes responsible for production of serotonin transmission (Cepoiu, McCusker, Cole, Sewitch, Belzile & Ciampi, 2008 p. 28).

Serotonin is involved in the transmission of impulses in the nervous system and its over/underproduction has been associated with cases of clinical depression. The nature of production of serotonin, dopamine and norepinephrine has limited research studies carried out in the area of the relationship between the levels of the neurotransmitters to cases of depression.

The levels of the neurotransmitters that are produced are minimal and the metabolites that result after the neurotransmitters are used up are insufficient to give conclusive information about the levels that are produced in depression patients and individuals who do not suffer from depression.

However, it is recommended that individuals who have genetic predisposition to depression should subject themselves to as reduced stress as possible. This is because such individuals already have a stress management system that is unreliable and it might not be able to cope with increased environmental stress.

The stress management systems of such individuals might be already stretched due to the occurrence of impaired body systems such as overproduction of cortisol hormone or irregular production of neurotransmitters in the body.

The impaired production of the needed amount of hormone and neurotransmitter levels is likely to lead to feelings of hopelessness and helplessness for individuals diagnosed with depression. One of the tests that are used for diagnosis of depression is by use of dexamethasone which is used to increase the amount of cortisol in the body (Ebert, & Ebmeier, 1998 p. 58).

For an individual with clinical depression whose endocrine system is impaired, the amount of cortisol produced would not be affected by the cortisol hormone levels introduced into the internal environment of the body.

After being tested, such individuals would still have high levels of stress hormone in comparison to an individual who do not have depression whose bodies would reduce cortisol hormone levels produced so as to utilize the amount already in the blood.

Individuals who are diagnosed with depression should be treated through regular sessions with a qualified psychiatrist and with approved medication in the market such as Cyambita, Lexapro and Zoloft (Fournier et al, 2010 p. 48).

Reference List

Bradshow, L. & Mattingley, B. (1995). Clinical neuropsychology. New York: Academic Press.

Cepoiu, M., McCusker, J., Cole, G., Sewitch, M., Belzile, E. & Ciampi A. (2008). Recognition of depression by non-psychiatric physicians—a systematic literature review and meta-analysis. 23(1):25–36. Journal of general Internal medicine. Springer. Retrieved from

Cutter, J., Norbury, R. & Murphy, G. (2003). Oestrogen, brain function, and neuropsychiatric disorders. Journal of Neurology, Neurosurgery and Psychiatry. 74(7): 837–40.

Ebert, D. & Ebmeier, P. (1998). New Models for depression. Switzerland. Advances in biological psychiatry. Karger Publishers.

Fournier, C., DeRubeis, J. & Hollon, D., et al. (2010). Antidepressant drug effects and depression severity: a patient-level meta-analysis. Journal of American Medical association.303 (1): 47–53.

Gelder, M., Mayou, R. and Geddes, J. (2005). Psychiatry. Oxford medical publications. 3rd ed. Oxford. New York.

Gravetter, J. & Wallnau, B. (2008). Statistics for Behavioral Sciences. Ohio. Cengage brain.

Hays, D., Wells, B. & Sherbourne, D. (1995). Functioning and well-being outcomes of patients with depression compared with chronic general medical illnesses. Archives of General Psychiatry. 52(1):11–19.

Lambert, K. & Kinsley, C. (2011 ). Clinical Neuroscience: Psychopathology and the Brain. 2nd edition. New York: Oxford University press.

Monteleone, P. (2001). Endocrine disturbances and psychiatric disorders. Current Opinion in Psychiatry. 14(6):605–10.

Sheline, I., Gado, M. & Kramer, C. (2003). Untreated Depression and Hipocampal Volume loss. American Journal of Psychiatry.160. (8). 1516-18.

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