Schizophrenia - Explinations

Theories of what causes of schizophrenia.

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Biological - Genetics

Family/twin studies:

Suggestions have been made that link schizophrenia with genes in the chromosomes. if schizophrenia is passed via genetics then the best way of finding out would be to study twins. These studies aim to prove if the closer the genetics the greater the risk of a person having schizophrenia. If it is passed through genes then it would show that schizophrenia is caused by a rare genetic mutation.

Kendler et al (1985) found relatives to those with schizophrenia are 18 times more likely to get schizophrenia compared to the general population.

Gottesman (1991) found if both parents have schizophrenia then there is a 46% chance the children will develop it. A concordance rate of 16% if only 1 parent have schizophrenia and 8% chance if a sibling has it.The concordance rate of MZ twins is 48%, DZ twins are 17%.

The chance of the general population developing schizophrenia is 1%. It is also suggested that the increased risk in families is due to the shared enviroment rather than genes

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Biological - Genetics cont.

Adoption studies

These studies looked at children with schizophrenia and compared them to their adoptive and genetic parents.


Tienari et al (1991) found out of 164 adoptees, 11 (7%) whose biological mother had schizophrenia were also diagnosed with schizophrenia, compared to 4 (2%) out of 197 controlled adoptees. This suggests a strong genetic link for the cause of schizophrenia.

However, Wahlberg et al (1997) examined the data used in Tienari's study and found a strong interaction between genetics and enviroment. Children adopted into families with poor communication had increased risk of becoming schizophrenic.

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Biological - Biochemistry

It is suggested that schizophrenia can be the result of excessive dopamine levels in the brain. It is also suggested that schizophrenia could be because the neurons in the brain are oversensitive to dopamine, overloading the neurons and result in many of the positive symptoms (e.g. involuntary movements, delusions and disorganised speech).


Post mortem show elevated levels of dopamine, but the cause and result are unknown.

PET scans also show higher levels of dopamine in the brain, but again the cause and result are unknown.

Anti-psycotic drugs that lower the level of dopamine are not always effective, especially when used on patients with negative symptoms. This suggests that a faulty dopamine system is not always the cause of schizophrenia.

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Biological - Biochemistry

MRI scans show enlarged cavities in the brain which supply nutrients and remove waste in the brain. This has been linked to the negative symptoms of schizophrenia (Alogia, Affective flattening and Avolition).


Research has shown the link, Pahl et al (1990) looked at 50 studies and found abnormally large fluid filled ventricles in the brain.

Suddath et al (1990) found that in twins, one with schizophrenia and one without. 12 out of 15 of the schizophrenic twins had larger ventricles than the non-schizophrenic twin.

But this data only show correlation. The enlarged ventricles may cause or a result of schizophrenia. Lyon et al (1981) found that higher doasages of anti psychotic drugs lead to enlarged ventricles.

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Psychological - Psychodynamic

Freud argued that schizophrenia was the regression to the pre-ego stage, to try and establish ego control. Most adults with schizophrenia experienced harsh childhoods, with cold and unsurportive parents. The regression results in the loss of touch with reality and develope things such as auditory hallucinations.


Freud produced one of the first theories to the cause of schizophrenia, the regression to childhood before reality was properly gripped by children  explains why schizophrenia patients lose touch with reality.

However, there are many problems with his theory, children are curious about their surroundings, while many schizophrenic patients lack motivation and interest. Also many parents of schizophrenic patients are not harsh or unsupportive as freud suggested. Waring and Ricks (1965) found many mothers were shy, withdawn and anxiuos.

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Psychological - Cognitive

There are 2 factors linked to the tthe behaviour and experiences of people with schizophrenia.The impairment in the thought processes like perception, memory and selective attention. When they are thinking to themselves, they think the voice inside their head is from someone else - auditory hallucinations. The schizophrenic patients is also unable to filter information properly. They therefore let too much information in and develop delusional beliefs.


This approach explains why many positive symptoms occur. McGuigan (1966) found those with hallucinations had reduced activity in parts of the brain monitoring the inner voice.

But this approach fails to address the cause of negative symptoms. It also doesn't explain if the Cognitive Biases/defits are the cause or consequence of schizophrenia. Many with brain damage suffer problems with attention and have problems between memory and attention, but dont develop schizophrenia.

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Socio-culture - Family relationships - Double-blin

Some believe there are problems with communications within families of schizophrenia patients. Bateson et al (1956) suggested the 'Double blind hypothesis'. This is when parents give contridictory messages, they offer may express care, but at the same time seem critical e.g a mother telling her son she loves loves him, but then turns away in disgust. The result is self doubt and confusion and eventually withdrawal. This results in a situation where the successful result to one thing, leads to a fail to another, so they are automatically wrong whatever they decide to do. The fear of facing contridictory messages creates and conflict within the child. The solution to escape the conflicting messages is delusions.


Berfer (1965) schizophrenics recall high levels of DB messages than non-schizophrenics, but the recall may be affected by the schizophrenia. Liem (1974) found no difference between the communication of families with and with a schizophrenic. Living with a schizophrenic child is stressful and it is unknown whether schizophrenia causes the double blind or not.

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Socio-culture - Family relationships - Expressed e

High degrees of expressed emotions (EE) in families involve criticism, hostility and emotional over involvment. High levels of EE are found to influence relapse rates. Negative emotional climates (e.g. over protective mothers but critical fathers) leads to too much stress for the individuals coping mechanism.


The EE has more empirical support than the DB. This shows the importance of the family for schizophrenic patients. Kavanagh (1992) found schizophrenia patients living in high EE enviroments were 4 time more likely to relapse than those in low EE. The cause and effect of EE on schizophrenia is unknown, but there is a important link between them. Hogarty et al (1991) found that therapies that reduced EE significantly reduce relapse rates.

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