Biological explanation of depression

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  • Biological explanation
    • Genetic factors
      • Having a 1st degree relative is risk factor
        • 20% of such relatives have depression compared to 10% of population at large
      • 46% concordance rate in identical twins and 20% in Dz twins
        • Concordance rates are never 100% so there must be other factors. Nature vs. nurture.
          • Can be explained in terms of co-morbidity. Kendler found a higher incidence in twins when looking at depression and G.A.D compared to depression alone. This suggests that some disorders are a product of genes that underlie a number of disorders.
      • Genes as diathesis
    • Neurotransmitter dysfunction
      • deficiency of nor-adreanline and serotonin = depression
        • Post-mortem studies found increased density of nor-adreanline in depressed, suicide victims
          • Drugs that lower nor-adrenaline levels bring about depressive states while those that increase nor-adrenaline show anti-depressant effects.
            • Kraft et al - Significantly better than placebo.
        • Introduction of SSRI's confirm link
          • The link is not straight forward. Patients in remission were given amino acid that decreases serotonin levels. They then had a relapse in symptoms.
    • Must have some biological basis as it's so widespread
    • Hemmen suggests 4 aspects which support biological basis: physical symptoms, appears to run in families, success of anti-depressants, how some medication and injury gives rise to depression
    • Support from evolutionary theory that says it must have some adaptive value. Others in the social network would have offered support, therefore strengthening the indiviudal.

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