Biology 202, Spring 2005
Third Web Papers
On Serendip

Everyone can become sad at times. Emotion is a normal aspect of the human existence. If one loses a loved one, fails at an important task, or even just has a bad day, it is normal for that person to display feelings of sadness. Normally, these feelings can last from a few hours to a few days. However, in some cases, an individual's sadness will persist and not subside. This problem is called depression. If not treated, depression can become problematic for an individual's health, and eventually, develop into a life threatening illness (1). More than fifteen percent of people with depression commit suicide, and depression has also been know to increase the probability of heart attack and stroke (1).

Depression can affect anybody and can occur across all demographic variables; it can even occur in other animals. However, one aspect of depression that is extremely intriguing is the fact that its incidence is much higher in women than men. In the United States, there are a reported two women for every one man with depression. In the rest of the world, that rate increases to 3 to 1 (2). Some possible causes of this discrepancy have been noted, but there the exact causes and how they relate has not.

Although there is still much to be learned about the gender differences of depression, the scientific community has an fairly extensive knowledge of its general causes, both biological and environmental. However, it is still unknown how these causes relate, and what causes are the inherent initiators. This paper will discuss the different causes of general depression, and attempt to better understand how the causes of depression relate to one another. It will then classify the causes leading to the differences between males and females, and apply the principals of the analysis of the general causes in order to better explain why women are more prone to depression.

Generally, there are three major factors that can cause depression in individuals, and usually, it is a combination of these factors that ultimately leads one to depression (3). The three factors are genetics, neurobiology, and environment. It is disputed which one contributes the greatest towards causation, but there is a relative consensus on the fact that all three contribute to depression.

The evidence of genetic causation lies mostly in the fact that depression frequently runs in families. People with blood relatives that have had depression are more likely to become depressed themselves (1). These theories have been supported through studies on adopted children who's biological parents were depressed, as well as studies on twins (3). However, the exact gene or genes responsible for depression have not been found. Various regions of certain chromosomes have been targeted as locations of possible depression genes, but scientists are having difficulty pinpointing the exact gene(s). Some believe that this is due to the fact that multiple genes contribute a small portion to depression (1).

There probably isn't one depression gene, or even few genes devoted to depression. However, studies support that depression can be genetically caused. Therefore, it is most likely that there are some genes that trigger certain biological situations, which in turn can cause depression.

Biologically, there are both neural and hormonal areas linked to depression. The neural areas involve monoamine neurotransmitters such as serotonin and norepinephrine (1). Serotonin is found throughout nature, but when acting as a neurotransmitter in the human brain, it plays a large role in mood and feelings of happiness (4). Depression can occur when there is a lack of serotonin in the brain (1). This is most likely due to the fact that the release of serotonin causes feelings of happiness. If serotonin is not released, then one does not feel as happy. Depression can also result when there is a lack of norepinephrine in the brain (1). Norepinephrine functions as a response to short-term stress. Most likely, a lack of it causes depression, because it helps one deal with short term stress. If there is a lack of norepinephrine then one cannot properly deal with stress, and high stress levels have been known to cause depression.

Neurotransmitters are not the only neurobiological areas active in depression, hormones, most specifically corticotropine, affect depression. Corticotropine plays a large role in flight aspect of the flight or fight model. It causes the release of other biochemicals that are released during the flight aspect of the model. These biochemicals cause repressed apatite for food and sex (1). People with depression often have large amounts of corticotropine. corticotropine is also stress responsive by causing feeling of stress (1).

It is difficult to tell whether these biological causes of depression are initiators or only pathways from other genetic or environmental factors that initiate depression. What is known is that depression always occurs through neurobiological responses, and can be cured chemically. Therefore, it can be assumed that it is the final step from initiator to depression. It is most likely that genetics or environmental factors cause these neurobiological factors in one way or another.

The environment definitely plays a role in depression. As stated, high stress levels can cause one to become depressed. Anxiety can as well (2). Life events, such as traumatic childhood experiences can lead to depression in adulthood (1). Romantic breakups also tend to cause depression is some individuals (3). One of the most prominent environmental factors is lack of achievement, direction, or freedom in one's life. Many people who do not achieve the success they hope; do not have a plan for themselves or know where they want to be; or, are stuck in situations where they cannot leave, become depressed (2). Ultimately, there are many environmental factors that can lead to depression. However, these situations do not cause depression in everyone. Therefore, I contend that these environmental factors may trigger depression, but there are other genetic or biological factors that must be involved.

A causal study of depression is a difficult one. The major factors leading to depression have been located and thoroughly studied, but the role in which each factor plays in causing depression is almost totally unknown. Therefore, currently, a philosophical approach to the way in which the brain, mind, and environment work is the only means to shed light on how a person becomes depressed.

First, it must be understood that the nervous system can perform the same function in many different ways (6). Therefore, because depression always occurs in some way neurobiologically, it can be interpreted that depression can be caused in many different ways. Furthermore, the neurobiological aspect of depression is the most essential, because no matter if it is initially caused biologically, environmentally, or genetically, depression changes the brain and can be treated with chemicals that directly effect the brain. All people who are depressed have biochemical changes (1).

In assessing the relationship between causes, it is best to start at the source of depression (neurobiology) and move out, towards the initial cause. I contend that in many situations of depression either genetics or environmental factors, or both initiate the depression, and cause neurobiological changes that cause depression. However, the fact that the nervous system can manipulate behavior without inputs suggests that the nervous system can cause depression itself. But why? I believe that the everything in nature has a purpose; therefore, if the brain manipulates itself in a way that causes depression, it is done with a purpose. Maybe depression is a result of other changes the brain needs to perform; similarly, maybe the brain needs to be depressed in order to perform certain tasks. Many people who are depressed experience enhanced creativity and learn more about themselves and others (7). It is possible that the brain could put itself into depression in order to enhance specific types of learning and application.

Not only could the unconscious brain be responsible for initiating depression, but the I-function could as well. A person could want something that causes depression. For example, a person may want to be more creative, and in result becomes depressed to do so. However, in these situation other environmental factors would be present

The environment, as well as genetics can affect the nervous system to cause depression, but most likely it is a combination of the two. As stated, many different environmental factors can cause depression; however, the same environmental factors will cause depression in some, but not others. Therefore, there must either be genetic disposition towards depression, or towards biological factors that cause depression. For example, a person might have genetically low serotonin levels; thus, when they go through traumatic experiences, they not only get unhappy, they get depressed. Genetics could also cause depression without any environmental stimulus. Little is known about the details of genetics role in depression, but what is known is that in some people genetics plays a role in their depression, and in others it does not (1).

Ultimately, since there is no solid evidence supporting one factor inherently causing depression over the other, as of now, it must be left at the theory that either of the three can inherently cause depression. However, because there is evidence to support that neurobiological factors are always involved (1), and also, there is evidence to support that brain equals behavior (6), there are four possible ways that depression can arise. 1. The nervous system by itself can cause depression. 2. Genetic predispositions can cause neurobiological changes that cause depression. 3. Environmental factors can cause neurobiological changes that cause depression. 4. Any combination of the three. However, what is most important is that biology is the essence of the causes of depression. Environmental triggers must be accompanied with biological situations in order to cause depression, because the same environmental input does not always lead to depression.

Hopefully, this can be properly related to the male and female differences in depression. As stated, women become depressed twice as often as men (8). This discrepancy is real, but because depression occurs in many different ways, there are many explanations for this gender difference.

Some explain the difference through more practical reasoning. For example, women are much more prone to diagnosing themselves as depressed, or reaching out for help. However, this explanation can not account fully for the discrepancy, because it has been noted that females attempt suicide much more often than males. Also, men would rather not reach out for help and deal with their problems through substance abuse or activities, while women would dwell on their issues (8). Another theory is that men become depressed over different things than women, and the things that women get depressed over occur more frequently. However, this theory has been unsupported, and there is evidence that shows that men and women become depressed over the same issues; only women become depressed more often (9).

Others try to account for the discrepancies in incidence through environmental factors. The most prominent theorized cause is the social status of women. Women have less freedom than men do, and can not always do as they please (2). This may cause an increased need for emotional support that if women do not get, causes to depression (10). Furthermore, women have higher chance of depression right after childbirth. This has been explained socially by the fact that after childbirth women realize that they cannot aspire to do anything else, but care for their children (2). This makes sense, since both women and men become depressed due to failing aspirations and career problems (9).

Finally, the last group of reasons for the discrepancy is biological. Studies have indicated that during a menstrual cycle, women have a greater release of hormones in their HPA axis, which is responsible for the release of corticotropine (2). Furthermore, women do not have the same ability to shut off the production of stress hormones as men, because women's sex hormone blocks their ability to do so (10) . Therefore, women get stressed more easily, and this can leads to more depression. This could very well account for depression during and after pregnancy, because hormonal levels increase. Also, although it has not been confirmed, it has been suspected that there is a gene on the X chromosome that causes depression (1).

Ultimately, like there are many theorized causes of depression in general, there are many different theorized causes for the greater incidence of female depression. Also, these differences follow generally the same factors: biology/genetic and environmental causes. However, just as in the causes of depression in general, biology is the essence of the difference between male and female depression. Whether or not the causes are classified as biological or environmental, they are inherently biological, and all relevant causes can be biologically explained.

First, the social status of women is biological. If they are repressed, they are because they are biologically weaker then men. If they must cope with motherhood, it is biological, because women were biologically chosen as mothers, and men as fathers. Furthermore, if women are more depressed, because they can not aspire to achieve what men can, it is biological, because their biological roles in human the human existence has not allowed them to do so. Ultimately, because brain equals behavior, and depression is a behavior, every argument pertaining to the male-female discrepancy is inherently biological. The same goes for the causes of depression in all individuals.

In conclusion, many explanations can be made about how one becomes depressed, both biological and environmental. However, reduced to its pure form, all of the causes are biological, and the environmental factors, are only result of deeper biological meanings.

References

1)The Neurobiology of Depression

2)Gender Differences and Depression

3)Causes of Depression

4)Serotonin

5)Norepinephrine

6)Neurobiology 202 Lecture

7)Depression...Or Better: Thinking About Mood

8)Depression in Women

9)Men and Women Are Not Worlds Apart After All

10)The New Sex Score Card


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