PSYA4 Depression Essay 2 - Biological Explanations

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Hi. This is the second essay out of five that could come up. I have also done the other five. I really hope this helps :)

Essay 2:

Describe and evaluate bioloigical explanations of ONE mental disorder (Depression) (8+16)


  • Depression does run in families and this suggests that there is a genetic componant to the disorder. Therefore, concordance rates in twins have been investigated.
  • Concordance rates in Monozygotic (MZ - from the same egg) and Duozygotic (DZ - two eggs) have been investigated. For bipolar disorder, concordance rates are 60% for MZ twins and 20% for DZ twins. For unipolar disorder, concordance rates are 46% for MZ twins and 20% for DZ twins. 
  • The diathesis-stress model attempts to explain behaviour as a predispositional vulnerability together with stress from life events. It helps to explain a genetic vulnerability to depression. 

+ Studies into genetics suggest evidence for the diathesis-stress model where individuals inherit different levels of predisposition to developing depression. 

- Twin and family studies don't consider the fact that they share a socio-psychological environment. Because concordance rates are not 100% we can conclude that there are other factors than genetics when it comes to depression. 

Amine Hypothesis:

  • The Amine Hypothesis suggests that depression is caused by a low activity of monoamine neurotransmitters (noradrenanline, serotonin and dopamine). They act as chemical messengers between the endocrine and nervous system and are assocaited with reward and punishment. The hypothalamus connects them and is involved in areas that are affected by depression (sleep, appetite, sexuality).
  • Evidence for the amine hypothesis can be found in drugs. Monoamine Oxidase Inhibitors (MAOI's) increase noradrenaline and decrease depression symptoms. Reserpine (a drug to control blood pressure) depletes levels of noradrenaline and leads to depression. Prozac increases levels of serotonin and relieves depression.

- The effect of drugs is not immediate, although neurotransmitter levels are altered immediately…


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