Biological Explanation of Schizophrenia

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  • Biological Expalnations of Schizophrenia
    • Twin Studies
      • Researchers can investigate genetic and environmental factors. Monozygotic twins (share 100% of genes) and Dizygotic twins (share 50% of genes). Mz more concordant in terms of Schiz traits than Dz.
      • Joseph (2004)- calcluated the concordance rate for Mz twins is 40.4% and Dz is 7.4%.
      • More recent, methodologicallysound studies using double blind techniques, report lower concordance rates for Mz twins. However, it still supports the genetic position, Mz concordance is still many times higher than Dz twins.
    • Adoption Studies
      • Analyse individuals who share genes but not their environment.
      • Tienari et al (2000)- Finland, 164 adoptees whos bio mothers have Schiz, 11 (6.7%) also recieved diagnosis of Schiz, compared to just 4(2%) of 197 control adoptees. CONCLUDED these show a genetic liability had been 'decisively confirmed'.
    • Dopamine Hypothesis
      • Dopamine is one of the neurotransmitters that operate in the brain. This hypothesis states the messages from neurons transmitting dopamine fire too easliy or too often, leading to characteristics of Schiz. Schiz thought to have abnormally high numbers of D2 receptors on recieveing neurons, resulting in more dopaminebinding and more neurons firing.
      • Dopamine plays a key role inguiding attention, so disturbances in this process may lead to problems with attention, perception and thought (Comer, 2003).
      • Amphetamines- is a drug with special relavance to Schiz. It is a dopamine antagonist, stimulating cells containing dopamine, flooding the synapse with it. Large doese of the drug can cause characteristics of Schiz e.g. hallucinations and delusions of a Schiz episode.
      • Antipsychotic drugs- they block activity of dopamine in the brain. they reduce the stimulation of the dopamine system, they eliminate Schiz symptoms. They alieviate the symptoms, which strengthens the case for this being a major contributing factor of Schiz.
      • Parkinson's disease- low levels of dopamine activity are found in people suffering with this problem. It is a degenerative neurological disorder. It was found that people who were taking the drug L-dopa which raised their levels of dopmine were experiencing Schiz like symptoms (Grilly, 2002).
    • Evaluation
      • Genetic factors
        • Family studies- shown schiz runs in families. However, it is accepted that this link of running in families may be due to rearing patterns or other factors, not genetics. Negative emotional climates can lead to stress beyond what the individual can cope with, which can trigger a schiz episode.
        • Twin studies- Asumption that Mz and Dz twins are equivalent, therefore greater concordance for Mz. However, Joseph (2004), Mz twins more likely to be treated more similarly and encounter more similar environments and experience 'identity confusion' Joseph believes the difference between concordance of Mz and Dz twins is nothing more than environmental differences.
        • Adoption studies- Assumption that adoptees are not 'selectively placed' ie adoptive parent6s who adopte a child from schiz parents are no different from adoptive parents who adopt child from normal background. Joseph (2004) claim this is unlikely, in countries like Denmark and the US, potential parents are informed of the genetic background of children prior to adoption. Kringlen (1987) 'Because the adoptive parents evidently recieved information about the child's biological parents, one might wonder who would adopt such a child.'
      • The Dopamine Hypothesis
        • Post-mortem studies- major problem is the drugs used to treat schiz by blocking dopamine can increase as neurons struggle to compensate for the sudden deficiency. Haracz (1982), in review of post-mortem studies of schiz found most of them had elevated dopamine levels had recieved antipsychotic drugs before death. those who hadn't recieved medication showed normal levels of dopamine.
        • Evidence from neuroimaging research- development of PET scans has allowed researchers to investigate dopamine activity more precisely.However, neuroimaging studies have failed as of yet, to provide convincing  evidence of altered dopamine activity in the brains of individuals with schiz (Copolov and Crook, 2000).



I know this was created quite a while ago, but I really don't understand the AO2 for adoption studies? Like what does knowing a childs background beforehand do for the biological explaination? 

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