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Schizophrenia (Biological explanations (The dopamine hypothesis…
Schizophrenia
Biological explanations
The dopamine hypothesis
Hyperdopaminergia in the subcortex (central areas), e.g. Broca's area, may lead to speech poverty / hallucinations.
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Neurotransmitter, particularly dopamine, important in functioning of symptoms implicated in schizophrenia.
Neural correlates
Negative symptoms
Avolition - motivation involves anticipation of reward, ventral striatum believed involved in anticipation.
Juckel et al:
- Measured ventral striatum activity levels.
- Lower levels in controls.
- Negative correlation between activity levels & severity of negative symptoms.
Positive symptoms
Allen et al:
- Scanned brains of people experiencing auditory hallucinations.
- Compared to control
- Lower activation levels in superior temporal gyrus & anterior cingulate gyrus of hallucination group.
Genetic basis
Runs in family
Gottesman: As genetic similarity increase, so does probability of sharing schizophrenia.
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Psychological therapies
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Token economy: Reward system used to reinforce socially normal behaviour to help patients rejoin society (institutionalisation).
Cognitive behaviour therapy: Challenge irrational thoughts & teaches patients to cope with symptoms such as delusions & hallucinations.
Evaluations
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Ethical issues with token economy depriving severe patients of privileges, leading to short term lower quality of life.
CBT challenges patients core beliefs, may be interfering with freedom of thought.
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Biological therapies
Typical antipsychotics
Chlorpromazine
1950s, tablets, syrup or injection.
Oral: maximum 1000mg, doses usually maximum 400-800mg
Acts as antagonist, blocks dopamine receptors in synapses to reduce activity.
Effective sedative, may be related to effect on histamine receptors.
Atypical antipsychotics
Clozapine
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Not in injection, daily dose 300-450mg.
Same function as chlorpromazine, but also works on serotonin & glutamate receptors.
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Risperidone
1990s, tablets, syrup or injection, daily 4-8mg,
Works as other drugs, though binds more strongly to dopamine receptors, more effective in small doses.
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Evaluation
Serious side-effects, including dizziness, agitation, sleepiness, stiff jaw, weight gain...etc.
Neuroleptic Malignant Syndrome, high temperature, delirium, coma & can be fatal.
Use of antipsychotics only based on dopamine hypothesis, of which there is mixed evidence.
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