PSYA4 Bio explanations of depression

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  • Biological Explanations of Depression
    • Genetic Factors
      • A01
        • Genetic factors is one explanation such as having first degree relatives with depression seems to be a risk factor for depression.
          • Studies have selected people who have depression and examined whether othe family members might or have depression. If there is a genetic link, the probands' relatives should show high rates.
        • Twin studies can also be used because identical twins (mz) should have all their genes in common and non-identical twins (dz) should have half. If the environment shared by the twins is roughly the same for both types of twins then it should be similar compared to fraternal pairs.
          • McGuffin studied 177 probands and their same-sex co-twins. The concordance rate was 46% for mz twins and 20% for dz twins which suggests that there is a genetic link.
        • Wender studied the biological relatives of adopted individuals who had been hospitalised for severe depression. She found a much higher incidence of severe depression in the biological relatives than in the biological relatives of non-depressed people.
      • A02
        • Concordance rate is never 100% which means there must be other factors involved in depression, it is a mixture of nature vs nurture.
        • A mutant gene that starves the brain of serotonin has been found to be 10 times more prevalent in depressed patients than in control individuals. Patients with the mutation, failed to respond well to SSRIs. This suggests that the mutation may underlie a treatment-resistant subtype of depression which could be used to explain biological aspects.
        • Lower genetic concordance rates for depression may be explained in terms of comorbidity. Kendler found an increase of mental disorders in twins when looking at depression and generalised anxiety disorder than when looking at depression alone. This suggest that some disorders like depression are a product of genes that underlie a number of other disorders.
    • Depressive disorders are the most common form of mental disorders, it makes sense that such a widespread disorder has some biological basis.
    • Hamman suggested different aspects to support the belief such as physical changes and that it may run in the family.
    • Neurotransmitter Dysfunction
      • A01
        • Deficiencies in noradrenaline  can be a cause of depression. Post-mortem studies show increased densities of certain noradrenaline receptors in the brain of depressed, suicide victims. When noradrenaline is scarce in the synapse receptors, numbers increase in density and try to pick up what is available.
        • Low levels of serotonin appear to cause depression. The introduction of prozac an other antidepressants that selectively block serotonin re-uptake confirm the association between low levels of serotonin and depression.
      • A02
        • There is a link between noradrenaline and depression. Kraft studied 96 patients with major depression who were treated for 6 weeks with a dual serotonin re-uptake inhibitor . Patients showed a significantly more positive response than those treated with a placebo. This suggests that lowering noradrenaline levels result in depression.
        • The link between serotonin and depression is not straight forward. Patients in remission from depression were given an amino acid that temporarily decreases serotonin levels in the brain, patients had a relapse in symptoms. This suggests that lowering serotonin levels results in depression. However, it doesn't induce depression in all people.
        • There may be an evolutionary perspective that supports the view that depression has a genetic basis because depression may be so widespread, it may be adaptive. Therefore, people in the social network are likely to provide support which strengthens the individual.


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