Biological Explanations of Uni-Polar Depression

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  • Created by: bethcx
  • Created on: 25-02-16 09:40
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  • Biological Explanation of Uni-Polar Depression
    • Brain Structure
      • Development in neuroscience and improved scanning techniques have found that dysfunction and abnormalities in the brain are associated with depression.
        • Frontal Cortex
          • It's important in maintaining beliefs about goals and the means to achieve them.
            • Drevets
              • Found that depression is associated with lower than normal activation in this area.
                • This means that they're less likely to believe they can achieve goals.
            • MRI scans have shown a reduction in the size of frontal lobes in depressed people.
        • Limbic system
          • Consists of a number of structures yhat are involved in motivation, mood, and emotions.
          • Amyglada
            • Part of the limbic system
            • It's to do with the reaction to threat and increased activation of this is seen in depressed individuals and is thought to affect their ability to process and judge 'threatening' information.
              • This over activation interprets information negatively and believes it to be worse than it actually is.
    • Genetics
      • Family Studies
        • Winkour
          • Found depression in just over 10% of first degree relatives, compared to only 4.9% of control relatives.
            • Earlier research found that up to 50% of the children of depressed individuals showed symptoms of depression,
              • However, living with someone with depression may lead to their child feeling isolated to due being shown little affection, meaning it could be down to environmental factors.
      • Twin Studies
        • McGuffin
          • Looked at over 200 pairs of twins. If a MZ twin had unipolar depression, there was a 46% chance the other one would. For DZ twins the concordance rate was 20%.
            • The concordance rate isn't 100% which suggests environmental factors
            • It's difficult to separate environment factors, expecially for twins who have been exposed to the same life experiences,
      • Adoption Studies
        • These eliminate environmental factors.
          • Wender
            • Investigated the families of adopted individuals in Denmark who had severe unipolar depression. The biological parents of depressed adoptees had a higher incidence of severe depression than the biological parents of non-depressed adoptees.
              • This means that only severe depression may be caused by genetic factors.
              • It's only on Danish individuals meaning it's not representative
    • Neurotransmitters
      • It's argued that low levels of the neurotransmitters serotonin (5-HT) and noradrenaline (na) reduce firing of neurons at the synapse causing symptoms.
        • McNeal
          • Found that cerebrospinal fluid in depressed patients contained less of a major 5-Ht by product, showing they have lower levels of this in their brains.
            • Similarly, byproducts of na are low in the urine of depressed patients.
        • The basic theory of there being low levels of 5-HT and na has been critisced as antidepressants raise levels of 5-HT and na within days but patients don't feel better for weeks- suggesting the cause is more complex.
      • Tryptophan is a precursor (building block) of 5-HT and is required for it's production,
        • Delgado
          • Found that a reduced tryptophan diet caused relapse in 67% of a group previously diagnosed with depression. They recovered when the diet stopped.


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