Analyze the biological etiology of Major Depressive Disorder:

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Analyze the biological etiology of Major Depressive Disorder:

This paper will analyze the biological etiology of major depressive disorder through research into related genetic, evolutionary and biochemical factors. Major depressive disorder is still a little understood disease, primarily because it is thought to be caused by a great number of factors from environmental (negative life events, stress, environmental change) to biological (hormones, neurotransmitters, and genetic predisposition). While it is not possible for psychologists or psychiatrists to attribute depression in any individual to a single cause, their understanding of the different factors can help them alleviate symptoms and suggest strategies for coping. The biological etiology is one facet of this understanding.

Research suggests that genetic factors can be used to partly explain the causes of major depressive disorder.  Nurnberger & Gershon (1982), for instance, conducted a review of seven twin studies and found that concordance rates were consistently higher among MZ twins (an average of 65%), when compared to DZ twins (averaged at 14%). The consistently higher concordance in MZ twins indicates that genetic factors may play a role in predisposing an individual to major depressive disorder. Duenwald (2003), for example, has recently suggested that a short variant of the 5-HTT gene may be associated with a higher risk of depression, as it plays a role in serotonin pathways – which have been linked to controlling mood, emotions and sleep.

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The fact that concordance rates for MZ twins in Nurnberger & Gershon (1982) is significantly below 100%, however, indicates that genetic factors do not give us the whole picture. Therefore, despite higher concordance rates in MZ twins, it is clear we cannot rule out the influence of the environment. It is also worth noting that the data of Nurnberg & Gershon (1982) are correlational, and therefore do not show that the genetic factors cause depression. Capsi et al. (2003) for instance suggest that genetic factors could moderate responses to environmental factors. This is best explained by the example that long term ...

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