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Biological explanation of schizophrenia: dopamine hypothesis
The positive symptoms of schizophrenia are caused by too much activity in the
dopamine pathways. This is caused by having too many D2 receptors. Dopamine
neurons affect attention which could account for the disturbances in attention,
perception and thought processes.
Amphetamines increase levels of dopamine as they stimulate dopamine
neurons to release dopamine into the synapse. These can lead to
hallucinations and delusions and can cause other positive symptoms. This
shows that high activity in dopamine pathways can lead to positive symptoms
Some people who suffer from Parkinson's disease are given a chemical called
L-Dopa which increases dopamine levels as they don't have enough dopamine,
leading to them to show some symptoms of schizophrenia. This shows that
high activity in dopamine pathways can lead to positive symptoms of
Phenothiazines (antipsychotics) block the dopamine receptor and reduce the
attention deficit in schizophrenia. This suggests that D2 receptors increase
activity in dopamine pathways and can lead to positive symptoms of
Only explains the positive symptoms (simplistic): the new atypical
antipsychotics also influence serotonin levels and are slightly more
effective at treating the negative symptoms. This shows that the symptoms
of schizophrenia have multiple causes.
Deterministic nature of explanation can lead to useful treatments: the
dopamine hypothesis is deterministic because there is no free will over
having too many D2 receptors in the brain and therefore having too much
activity there. This means that it is easier to treat for example if the extra
D2 receptors are blocked by a drug then the abnormal activity will go down.
Reductionist as it only focuses on dopamine: so other factors such as
ventricles and childhood experiences causing stress, therefore we can only
have a limited understanding of the cause of schizophrenia.
Correlational evidence: the evidence which supports the dopamine
hypothesis is only correlational. They show that dopamine is linked to the
positive symptoms, but they can't be used to support the idea that dopamine
activity is the cause of the positive symptoms.
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/ Relationship to genes: genes and dopamine activity may be linked and
ultimate genes may be the cause of schizophrenia whilst dopamine activity
would be the proximate cause.…read more