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Biological explanations for schizophrenia: genetic explanation
Suggests that one or more of our genes we inherit from our parents can put us at
risk of becoming schizophrenic.
Investigated the concordance rates between a schizophrenic individual and
their family of having schizophrenia.
Found that monozygotic twins, who have identical genes, only had a 48%
concordance rate of developing schizophrenia.
Whilst this shows that schizophrenia can be influenced genetically, it also
shows that other factors influence concordance rates, because if genes
were the single reason for developing schizophrenia then we would expect
concordance rates of 100%.
Also found that first degree relatives of the schizophrenic shares 50% of
their genes but have different concordance rates which further suggest
that other factors such as nurture affect the chances of developing
Unreliable as the study doesn't separate nature from nurture- the chances
of developing schizophrenia may also be due to the way a person was
brought up within their family. Therefore we can't be certain that all of the
48% concordance rates are due to the MZ twins identical genes.
Investigated the concordance rates for schizophrenia between MZ and DZ
Found that MZ twins had higher concordance rates than DZ twins. MZ
twins had a concordance rate of 39% whereas DZ twins had a concordance
rate of only 5%
This shows that genes play a big role in explaining schizophrenia as DZ
twins have lower concordance rates than MZ twins, because DZ twins only
share 50% of their genes, unlike MZ twins who share 100%.
This further suggests that MZ twins have a higher chance of developing if
their twin has schizophrenia.
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Conflicting evidence- genetic influence of MZ twins varies between studies.
Gottesman showed concordance rates as 48% whereas this study showed
them as being only 39%. Therefore results are unreliable due to the
differences so we cannot be sure that genes do affect the chances of
Kety et al
Studied siblings who were separated then adopted.…read more
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Lack population validity- only taken place in Finland. Therefore results
cannot be generalised to other countries as those countries may use
different books to diagnose schizophrenia, meaning the findings would not
be valid when using different definitions of schizophrenia.
Only looked at the genetic link between children and mothers, not fathers.
Therefore we cannot be certain of the fathers genetic influence on the
chances of a child developing schizophrenia might be.…read more