Biolgical explanations of depression

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  • Biological factors to Depression
    • Genetic factors
      • that depression is inherited though genetic make-up
      • McGuffin et al
        • 177 sets of twins
        • concordance rate was 46%
          • suggesting a substantial heritable component
          • could be due to comorbidity
            • twins had the same childhood
          • higher than the general populations life time risk of developing depression
        • Having a first degree relative with depression increases a persons chances of becoming depressed
      • The Diathesis stress model
        • depression is caused by a pre-disposition eg a genetic link or a neurotransmitter dysfunction
          • we well as a stressor which triggers the depression
        • Kendler et al
          • Virginia twin study
            • women who had a pre-disposition to depression ie that had an identical twin who already had depression
              • more likely to devlop depression when faced with a negative life event than females with out the pre-dispostion
                • gender biased
                • reductionist
      • Suicidal gene
        • Royal Ottawa Hospital
        • Mutation in the gene that is a serotonin receptor
        • Suicidal tendencies were more common in people with the mutation on the gene
        • high every day life application
        • moral implications
        • Hrdina
          • long term study on 120 depressed Canadians
          • gene doubled the risk of suicidal tendencies
          • ignores social-psychological factors
        • cannot establish cause and effect
    • Biochemical factors
      • comer suggests depression is due to low activity of certain monoamine neurotransmitters
        • eg noradrenaline and serotonin
          • serotonin can be influenced by the sun
            • season affective disorder
        • neurotransmitters help to regulate the hypothalamus
          • crucial for the nervous and endocrine system
            • explains the disruption od sleep, appetite and physical movement
        • supported by the effectiveness of anti-depressants
        • Thase and Kuffer
          • anti-depressants reduced the symptoms of depression more than a placebo
        • Brunney at al
          • low levels of noradrenaline in depressed individuals
        • Delgado
          • depressed patients were receiving antidepressants were given a diet that would decrease their serotonin levels
            • while on the diet their depression symptoms returned and they went back to normal after going off the diet
          • however people with no pre-disposition show little mood change
            • rot et al suggest that a depressive episode alters the serotonin system and makes individuals more vulnerable
      • Cortisol hypersecretion
        • elevated levels of the stress hormone in depressed individuals
        • levels disappear when depression disappears
        • however Strickland found no evidence
          • however they did find high levels in individuals who'd experienced stressful life events
      • females areas twice as likely than men t develop depression
        • eg prementral syndrome and post-natal depression
          • Gotlib says that females who suffer postnatal depression have a pre-disposition
        • still only 10-15% of population
    • Evolutionary response
      • Adaptive
        • individuals experience higher levels of psychological functioning after than before hand
        • increases help and support
        • strengthens the individual
        • costly process

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