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Biological Explanations of Schizophrenia- Essay Plan
1. Describe in some detail the genetic factors- family studies- Gottesman found that
schizophrenia is more common among biological relatives of a person with schizophrenia and
also that the closer the degree of genetic relatedness, the greater the risk. For instance,
children with 2 schizophrenic parents have a concordance rate of 46%, children of one
schizophrenic parent 13% and siblings 9%. Although this could be due to common rearing
patterns or other factors not relating to heredity. Twin studies- Joseph calculated
concordance rates of 40.4% for MZ twins and 7.4% for DZ twins. Adoption studies- Tienari-
164 adoptees- bio mothers diagnosed as schizophrenic found that 6.7% also got same
diagnosis, as opposed to 2% of the 197 controls, conclude that the genetic liability to
schizophrenia had been "decisively confirmed".
2. Describe in some detail the dopamine hypothesis- messages from neurons that transmit
dopamine fire too easily or too often which leads to the characteristic symptoms of
schizophrenia. Schizophrenics seem to have abnormally high levels of D2 receptors on
receiving neurons which results in more dopamine binding and so more neurons firing.
3. Evidence for Dopamine hypothesis- Amphetamines- dopamine agonist- stimulates the nerve
cells causing the synapse to be flooded with the dopamine; large doses of this drug give
similar effects of a schizophrenic episode. Antipsychotic drugs- block activity of dopamine in
the brain, done by reducing stimulation of the dopamine system, eliminate symptoms like
hallucinations and delusions, therefore this provides strong evidence for dopamine being a
significant contributory factor for this disorder. Parkinson's disease- low levels of dopamine
activity are found in Parkinson's disease sufferers- Grilly found some people who were
taking the drug L-dopa to raise their levels of dopamine were developing schizophrenic type
4. Enlarged ventricles- Torrey found that on average the ventricles of a schizophrenic are about
15% bigger than normal people.
5. Critical Point 1: There is a methodological flaw with the majority of the studies carried out on
MZ and DZ twins. Joseph points out that it is widely accepted that MZ twins are treated more
similarly, encounter more similar environments and experience more "identity confusion"
than DZ twins. Consequently, there is a question of whether the differences in concordance
rates between MZ and DZ twins is down to nothing more than the environmental differences
that distinguish the two types of twin.
6. Critical Point 2: There is evidence to suggest that schizophrenia is an ancient disorder. Torrey
found schizophrenics in Australian Aborigines who lived about 60,000 years ago. The
evolutionary adaptive explanation for schizophrenia is that schizoid personalities have acted
in the past to perform the valuable function of dividing tribal communities when they become
too large so it helped to maintain dwindling food resources. Stevens and Price suggest that
maintaining schizoid symptoms would lead to the splitting of communities and the formation
of new ones. This is due to the fact that schizoid symptoms like mood changes, bizarre
beliefs, hallucinations and delusions of grandeur would induce discontented group members
to leave. This supports biological explanations for schizophrenia as an evolutionary
explanation is considered a biological explanation especially as it implies an adaptation that
would be beneficial to humans.
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Critical Point 3: There is a flaw with one of the key pieces of evidence to support the
dopamine hypothesis. The drugs used to treat schizophrenia by blocking the dopamine
receptors can actually increases it as neurons struggle to compensate for the sudden