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Discuss two or more biological explanations of schizophrenia (24 marks)
The biological approach assumes that schizophrenia has an organic cause, though this does not ignore
any psychological factors that may play a part in the onset of the disorder. There may be a
`diathesis-stress' relationship whereby a biological predisposition develops when significant
stressors are present in a person's life. The explanations which will be argued are genetics and
There exists research to point towards a genetic explanation of schizophrenia running in families,
because the closer the genetic relationship, the greater chance of them developing the disorder.
Gottesmann (1978) found that although the general population has a 1% rate of schizophrenia, the
likelihood of a first degree relative having the disorder is 12%, when two parents have the disorder
the chance is 40%, though schizophrenia occurs between cousins and nephews at a rate of 2-3%.
Overall, Tsaung suggested that if a stringent criteria is used, having a schizophrenic relative increases
the chance of it developing by 5-20 times than having no relatives with the disorder.
There are methodological issues with the family studies as they are low in population validity
because they usually have a small sample size and only a select number of families are selected. This
can mean that the results can't be extrapolated to the general public. Furthermore, in family studies it
can be hard to distinguish whether something is being caused by nature or nurture as families share a
On the other hand, support for family studies comes from twin studies where it assumed that
identical twins (MZ) have a higher concordance rate than fraternal (DZ) twins, indicating a degree of
inheritability. Gottesman and shields (1972) found a 42% concordance rate in identical twins, as
opposed to a 9% in fraternal twins, highlighting how research into this area has academic credibility.
Though there are problems using twin studies because if there exists a genetic inheritance in
schizophrenia, it's reasonable to assume a 100% inheritance, leading us to assume that only a
predisposition is passed on. Joseph would argue that the differences in concordance rates between
MZ and DZ twins are due to environmental differences, thus twin studies don't distinguish between
nature or nurture because they share the same environment.
Similarly, adoption studies have been carried out to test the genetic explanation. Tieniari (2000)
tested 164 schizophrenic adoptees in Finland born to schizophrenic mothers. 11 also received a
diagnosis of schizophrenia, compared to just 4% of 197 control adoptees. This led Tieniari to
conclude that the findings showed a genetic liability to schizophrenia.
However, thie study can be seen as culture bias as it uses adoptees from Finland and so the results
can't be extrapolated to other cultures.
In conclusion for the genetic explanation of schizophrenia, all of the research suggests a genetic
element of schizophrenia making the research reliable. But despite all of the above research, 2/3rds
of schizophrenics have no relatives with the illness. This argument can't explain why or how they
don't have it, therefore the explanation is incomplete because it's a reductionist argument to ignore
any other influences. It's reductionist because it ignores the role of nature, but a predisposition is
inherited allowing for the role of nurture in the explanation.
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The second explanation is the dopamine hypothesis which suggests that schizophrenia develops due
to the sensitivity and density of dopamine receptors. Weinberger (1987) claimed that schizophrenia
is due to the over activity and underactivity of the pathways in the midbrain linking to the limbic
Supporting evidence for the dopamine hypothesis comes from Wong et al (1986) who carried out
PET scans in schizophrenics taking phenothiazines, none and a control group of people without