Biological Explanations Of Depression

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The biological explanations for depression centre on the mood disorder being biologically caused. Genetic factors suggest that you are born with a biological weakness which makes you unable to resist stressors, which consequently leads to depression. This is known as the diathesis stress model. The main piece of research that supports this comes from the Maudsley Hospital twin register, where concordance rates of 46% were found in MZ twins and 20% in DZ twins. This suggest that depression must be passed on through genes if there is a high concordance rate between twins which share the same genetic makeup both having depression. However, biological factors such as the amine hypothesis states that if amines such as serotonin and noradrenalin become unbalanced, they can lead to depression. PET scans support this idea as they show that low levels of serotonin are present in people that are depressed. Other supporting evidence is that drugs such as MAOI’s, which work by increasing the available amount of noradrenalin in the brain, were found to be effective in alleviating the symptoms of depression. A problem with this is that it doesn’t state whether it is cause or effect. Significant support for the biological explanation of depression comes from neuroendocrine factors. Cortisol levels are higher in depressed people. A stress reaction leads to the production of Cortisol, a key hormone in arousal. In normal people a mechanism prevents excessive or prolonged arousal in response to a stressor. In depressed people those levels are high and then go down after a depressive episode. When noradrenalin levels are low, the Cortisol levels can’t be regulated which suggests that it is linked to depression. A problem with this explanation is that it doesn’t state whether it is cause or effect. There is significant evidence to suggest that the role of hormones, (primarily
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