Biological explanations for bipolar disorder

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  • Created by: bethcx
  • Created on: 18-02-16 17:31
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  • Biological Explanation
    • Neurochemicals
      • High levels of noradrenalinehave been implicated in mania.
        • Post found raised levels of neuroadrenaline in the cerebrospinal fluid of patients with mania, compared to controls.
        • Tenner found that manic symptoms subsided in patients after taking reserpine, a drug known to reduce noradrenalinelevels.
      • Mania is associated with low levels of serotonin, like depression.
        • This has led to the permissive theory of mood disorders. This is the belief that low serotonin activity sets the stage for a mood disorder and permits noradrenalinelevels to determine its particular form.
    • Genetics
      • It is believed that people inherit a predisposition to develop abnormalities that cause bipolar disorder.
        • These abnormalities include- decreased amount of glial cells in the prefrontal cortex, reduced activity in the prefrontal cortex, a decreased number of neutrons in the hippocampusand a decrease in size of the cerebellum.
      • Family studies have found that close relatives of people with bipolar have around a 7% chance of developing the disorder, compared to 1% of the general population.
        • Gershon found that relatives of bipolar patients have a 10-25% risk of developing a mood disorder, but not necessarily bipolar.
          • These results suggested that unipolar and bipolar disorders are the result of the same underlying problem.
        • The concordance rate for MZ twins is 70%, and for DZ twins it's 23%.
          • Evaluation: concordance rate not 100%, twins have same upbringing (environmental factors)
      • Some studies have linked bipolar to genes on the X chromosome.However these findings have failed to be replicated.
        • The current belief is that the disorder i polygenic- it's caused by defects in a number of genes, rather than a single one.

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