Aetiologies of Schizophrenia



Schizophrenia is a mental disorder which carries positive, negative and secondary symptoms. 

We have different explatations for schizophrenia. 

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Twins (Genetics)

One explanation is that schizophrenia is a genetic illness, this can be measured in various ways. 

One way= identical twins. 

Rosenthal (1963)- studied identical quadriplets who all developed schizophrenia but at different ages and with different symptoms.This suggested that schizophrenia has an inheited element. 

However, the girls had a terrible upbringing which may have effected their mental/emotional state abd so making them more prone to mental disorders. 

Both the mother and father showed signs of instability which supports the idea that the girls inherited it from them. 

Case study= cannot generalise to the rest of the population because evidence from such a small sample of quadruplets would not be apparent in every other individual. 

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Family Studies

Peoples who parents has an identical twin with schizophrenia had a 17% chance of being schizophrenic themselves with first cousins only having a 2% concordance rate (Gottesman 1991).

In family and identical twin studies it's hard to seperate the effects of the environment on genes and so results can be invalid. 

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Adoption Studies

Away to seperate genes and the envirnement.

If a child has a high concordance with their birth families as opposed to their adopted families, it would suggest a genetic basis.

Whereas if they have more in common with their adopted family it would be due to the environment. 

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Tienari (2002)

Studied 164 adoptees whose biological mothers had been diagnosed with schizophrenia.

Found that 6.7% also received a diagnosis.

Suggests a genetic basis.

Findings also show that children who are at a high genetic risk so well if their adopted family provide a supportive environment. 

So the environment and genes appear to work together. 

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Pointed out that MZ twins are treated similarily and encounter similar environments therefore concordance rates reflex this. 

Said that concordance rates are higher for non-identical twins than for their siblings despite being raised in the same environment.

Suggests something in the environment causes schizophrenia 


Theres something special about twins. 

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Issues with concordance rates

Genetics causing schizophrenia:

we would expect concordance rates with identical twins to be 100%, but it's more like 20-45%, so something else must be happening. 

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Seidman (1983)

Proposed that schizophrenia is caused by excess levels of the neurotransmitter dopamine. 


  • Chloropromazine blocks dopamine recepters, which is a useful treatment in schizophrenia. 
  • L-dopa increases dopamine levels which will produce sysmptoms of schizophrenia. 

Difficult to assess the levels of dopamine in the brain and is usually done in post mortems. This means evidence lacks reliability because for theories to be true the patient would have to be alive.

Lindstrom et al (1999)- found that blocking dopamine activity can actually increase it as neurons struggle to compensate for the sudden deficiency. 

It may also be that rather than the increasing of dopamine sensitivity causing schizophrenia, the schizophrenia causes an increase in dopamine sensitivity. 

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Psychological Theory- Freud

Argued that principples of the psychodynamic approach causes schizophrenia.

Conflict in personality (between the ego, id, superego) results in the individual regressing back to infancy.

This confusion results in schizophrenia. 

There is no evidence to support this and Sterling and Hellewell (1999) actually said that schizophrenic behaviour is not similar to infantile behaviour. 

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Psychological explanation- Social Factors

Some theories argue that there are abnormal and inadequate patterns of communication within schizophrenic families.

Bateson (1956)- Double Bind Theory which explains this. 

Problem= lack of evidence to support this theory.

Beryger (1965)- found that schizophrenics reported a higher rate of recall of Double Bind statements by their mothers than non-schizophrenics. This evidence lacks reliability as recall may be affected by their schizophrenia. 

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Expressed Emotion

Explanation of expressed emotional can also lead to relapse.

Families who engage in it show high levels of criticism, hostility and emotion over protectiveness.

Kauanagh (1992)- families with high expressed emotion are four times more likely to relapse. 

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Stress could cause schizophrenia. 

Birley (1968)- studied schizophrenics and found that they reported twice as many stressful life events compared to a control group.

Not all evidence supports this theory. 

Van Os et al- found no link, and in a prospective study found that stress actually makes you less likely to relapse. 

The 'diathesis stress' suggestion accounts for both genetic and environmental factors.

It suggests a physiological predisposition for schizophrenia only developing into a disorder if other significant psychological stressors are present in the persons life (Gottesman and Reilly 2003) 

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