Outline and evaluate biological explanations for schizophrenia

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Outline and evaluate biological explanations for schizophrenia

There appears to be a tendency for schizophrenia to run in families. This suggests that genesplay a role. The closer the genetic relationship the more likely the people are to share thedisorder. Evidence from family studies by Gottesman showed that when both parent areschizophrenic then there is a 46% chance of the child getting it, however, if only one parenthad it, it dropped to 16% and dropped to a further 1% when the sibling of the child hadschizophrenia. This suggests that a genetic factor is involved. Gottesman also looked atschizophrenics whose father had an identical twin. He found that there was a 17% of beingschizophrenic when the father was but he also found that there was also 17% chance of developing the disease when the father’s twin had schizophrenia but the father didn’t.MZ twins share 100% of their genes; DZ twins share 50% of their genes. If genes are a factor we would expect more identical twins to share the disorder than non-identical. Rosenthal tooka case study which had a set of female quadruplets. They all developed schizophreniaalthough the onset and symptoms were very different. This could have been a result of havinga troubled upbringing. This suggests a strong heritable component.However, most first degree relatives and twins share the same or similar environments so it isdifficult to separate genetic and environmental influences. Adoption studies compare peoplewho have been raised in a different environment from their biological relatives. If they havesimilarities with their biological relatives this should be due to genes. Evidence from adoptionstudies, such as, Tenari’s study that had a longitudinal study of 155 schizophrenic motherswho gave up their children fro adoption. These were compared with 155 adopted children whodid not had a schizophrenic mother. Once these children reached adulthood there was a10.3% chance of developing schizophrenia when the mothers also carried the diseasewhereas the children who had healthy mothers only had a 1.1% chance of gettingschizophrenia.This suggests genes rather than the environment have caused the disorder in these cases.However, adopted twins may still have shared similar environments. Even when the adoptedenvironments are similar there is still the shared experience in the womb and at birth so pre-natal viruses or birth trauma may have had an effect.Overall the evidence suggests that genes play a part but nature cannot completely explainschizophrenia as there is not a 100% concordance rate. Nurture needs to be considered andthe evidence suggests environmental factors must play a part. Without knowing the specificgenes involved we can’t explain how these contribute to the development of schizophrenia,however the current advances in research into the mapping of genes may bring more insightto the process.Schizophrenia has also been explained by brain chemistry. There are certain chemicalabnormalities that can be observed to produce schizophrenia-like states. For example,prolonged use of LCD or antabuse which is a drug used for alcoholism. Genetics may havean effect through body chemistry.The original dopamine hypothesis suggested that schizophrenia is associated with an excessof the neurotransmitter dopamine causing neurones to fire too often and transmit too manymessages. A more recent version says that rather than an excess of dopamine it is an excessof dopamine receptor cells that lead to more firing and excess messages. Dopamineneurones play a key role in guiding attention so disturbances in this process may lead to theproblems of attention and thought found in people with schizophrenia.Main antipsychotic drugs block the dopamine receptor cells and reduce symptoms, however not all schizophrenic patients respond to these drugs. L DOPA; a drug used to treatParkinson’s disease increases dopamine levels has a side effect which is similar toschizophrenic type symptoms. However not all individuals treated with these drugs developthe side effects. Amphetamines and LSD increase dopamine alongside symptoms of schizophrenia. Again, not all patients respond to the antipsychotics with reduced symptoms and not all individuals taking L DOPA and amphetamines develop schizophrenic type symptoms.

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Post-mortems on schizophrenics have shown unusually high levels of dopamine, especially inthe limbic system (Iverson, 1979). Seeman (1987) reviewed a number of studies and found a60-110 increase in dopamine receptor cells in schizophrenics compared to controls. Wong(1986) found twice the increase in dopamine receptor cells in untreated schizophrenicscompared to normal controls and untreated schizophrenics.Methodological issues for the twin and adoption studies include the fact they are often smallsample as MZ twins are relatively rare in the population. With Gottesman’s study there wereonly 12 pairs of twins that have been reared apart. Adoption sample do tend to have bigger samples which is ...

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