Aetiologies of Schizophrenia

  • Created by: VerrW
  • Created on: 25-05-15 17:15


Aetiologies of schizophrenia are the causes and consist of positive symptoms e.g. delusions and negative symptoms e.g. alogia. 

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Biological Explanation 1- Genes- Introduction

Schizophrenia is a genetic illness. This means that a gene or genes can be passed down from parents to children. It also predicts that like other genetic illnesses, it should run in families. 

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Biological Explanation 1- Genes- Twin Studies

Some of the most striking evidence for the genetic basis of schizophrenia comes from looking at concordance rates between MZ (identical) and DZ (non-identical) twins. A concordance rate is the relationship between the two twins and the extent to which both twins have the same disorder. 

The lifetime risk of schizophrenia in the general population is 1% therefore anything above this must be due to factors other than chance.

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Bio Explanation 1- Genes- Twin Studies- Rosenthal

Rosenthal (1963) studied quadruplets, in which all 4 girls were identical to each other. All of them developed schizophrenia, although they differed in terms of age of onset and their precise symptoms. They were known as the Genain twins. This provides evidence for strong genetic basis of schizophrenia.

However the girls had a terrrible upbringing where both the father and mother showed clear signs of instability and their childhood was disrupted due to the inability of the parents to properly care for the children. 

This supports the idea of a genetic basis for schizophrenia because the parents have a genetic disposition to develop schizophrenia and have issues and therefore poor childhood events have triggered it. 

However, it can't be 100% proven because it is impossible to isolate the role of environment and genes.The evidence presented is a case study, which means it is not representative and therefore it cannot be applied to others as it is a unique study of a small group. Additionally they are also biased

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Bio Explanation 1- Genes- Twin Studies- Evaluation

Joseph (2004) points out that a major issue with twin studies is that MZ twins are treated more similarly, encounter more similar environments i.e. more likely to do things together, and experience more 'identity confusion' (treated as 'the twins' rather than individuals) than DZ twins. Therefore the concordance rate of MZ and DZ twins reflect nothing more than the environmental differences that distinguish the two types of twins. 

However, Gottesman points out that the concordance rates for MZ twins reared apart are almost the same as for MZ twins reared together, thus suggesting a biological basis. It should be noted that often when MZ twins are reared apart they're still within the same family and often still have contact with each other and their birth parents. Therefore it is difficult to clarify the genes/environment issue.

Furthermore, this suggests that there is no free-will concerning the basis of schizophrenia and that a person's actions who suffer from schizophrenia are viewed as part of their conidition.

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Biological Explanation 1- Genes- Family Studies

Family studies have established schizophrenia is more common among gentic relatives of a person with the illness, and that the higher the percentage of genes you share with the sufferer, the more likely you are to get it yourself (Gottesman 1991).

For example, Varma et al. (1997) looked at the first-degree relatives (FDRs) of about 1,000 schizophrenics and 1,000 controls. The results showed that psychiatric illness was found in 16% of the FDRs of schizophrenics compared eith 7% of the controls. 

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Bio Explanation 1- Genes- Family Studies- Eval.

Many researchers now accept that family concordance for schizophrenia may be more to do with commom rearing patterns or other factors rather than heredity

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Biological Explanation 1- Genes- Adoption Studies

To overcome the issues of shared genes and environment, we can look at the concordance rates between adopted children and their birth families. If the children have a high concordance rate with their birth families as opposed with their adopted families, this suggests a genetic basis, whereas if they have more in common with their adopted family it would be due to environment

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Bio Explanation 1- Genes-Adoption Studies-Tienari

Tienari (2000) studied 164 adoptees whose biological mothers had been diagnosed with schizophrenia, and found that 11 (6.7%) also received a diagnosis of schizophrenia, compared with just 4 (2%) of 197 control adoptees (born to non-schizophrenic mothers). 

This again would suggest a genetic basis, however, an additional finding is that the children who are at a high genetic risk tend to do well if their adopted family provide a better supportive environment, better in fact than the ones who did not have a gentic risk but were brought up in poor environments. Thus suggesting that the environment and genes interact with each other and work together (diathesis-stress model). However adopted children are often placed in homes similar to their birth family making it difficult again to separate genes and environment. 

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Psychological Explanation- Stress/Life Events

Another explanation is that schizophrenia is caused by stressful life events.

Birley (1986) found by studying people who had experienced schizophrenia, that if they had a subsequent attack it was found that they reported twice as many stressful life events compared with a healthy control group. Therefore stress and life events are causing schizophrenics to relapse

However, Van Os et al. (1994) reported no link between life events and the onset of schizophrenia. Patients were equally likely to have had a major life event or not in 3 months prior to the onset of their illness (when assessed retrospectively). In fact, in a prospective part of the study, those patients who had experienced a major life event went on to have a lower likelihood of relapse

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Psychological Explanation- Stress/Life Events

Similarly Day et al (1987) carried out a study in several countries. They found that schizophrenics tended to have experienced a number of stressful life events in the few weeks before the onset of schizophrenia. 

However, there are alternative interpretations of Day et al's findings, one being was it the early symptoms of schizophrenia that caused the events e.g. losing job, relationship broken down. Or was it whether the life events e.g. losing your job etc that causes schizophrenia and triggers it. 

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Psychological Explanation- Stress/Life Events

Social Causation Hypothesis tries to explain why schizophrenia is much more prevalent in the lower social classes. This explanation argues that people in the lower social classes tend to experience more stressful lives because of poverty, unemployment, poorer physical health and so on. Stress is also likely because of social and racial discrimination. The high levels of stress makes people more prone to schizophrenia, thus providing a convincing argument that stress causes schizophrenia.

However, social drift hypothesis would suggest that it's the symptoms of schizophrenia that lead people to having more transient lives and not being able to function at a high level.

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Bio Explanation- Dopamine Hypothesis

Seidman (1983) first proposed that schizophrenia may be caused by excess levels of the neurotransmitter dopamine. A slightly different view is that the neurons in the brains of schizophrenics are overly sensitive to dopamine. 

The drug chlorpromazine has proved useful in the treatment of schizophrenia. The main reason for this seems to be that it blocks dopamine receptors and reduces the amount of dopamine, therefore supporting the view that too much dopamine causes schizophrenia. 

Lindstrom et al (1999) provides empirical evidence to support that dopamine plays an important role in schizophrenia who used PET scans to assess the levels of dopamine in the brain of the schizophrenic patients who had not received treatment and found that there was more dopamine than normal being produced. 

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Bio Explanation- Dopamine Hypothesis- Evaluation

It is difficult to assess the levels of dopamine in the brains of schizophrenic people. It is usually done in post mortem. However there is one indirect way which involves inserting a needle into the spine; a dangerous technique. Generally, the results from living patients do not seem to suggest that schizophrenics have a higher level of dopamine than others. 

Additionally, it is unclear whether dopamine levels cause schizophrenia or if schizophrenia causes high dopamine levels to rise. Therefore it is impossible to deduce which is the cause and which is the effect as they can't be examined before the illness. 

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Diathesis Stress Model

Is an interactionist perspective and suggests that people will have a biologically perceptivity so people might have a genetic disorder vulnerable to mental illness such as schizophrenia which lays dormant in them and appears when stress or a life event causes trauma and triggers the illness. Therefore it is nature interacting with nurture.

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Overall, it is over simplified to look at only a biological or social theory as no single explanation can explain every sufferer. Thus to offer effective treatment a more holisitc approach would need to be adopted by looking at all the possible causes in order to avoid reductionism.

Furthermore, if the biological perspective is adopted this would suggest that a schizophrenic would have a lack of control over their behaviour and therefore are not responsible for their actions. However this can cause implications for the justice system as it indicates that we have no free will over ourselves and the decisions we make.

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