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Hint
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Answer
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How can negative symptoms be explained by?
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Low levels of dopamine in the mesocortical pathway
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How can negative symptoms be explained by irregular serotonin activity?
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Serotonin regulates dopamine levels in areas such as the mesolimbic pathway so irregular serotonin activity changes the levels of dopamine.
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What other neurotransmitters might play a role in schizophrenia?
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GABA and glutamate
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Strengths of this theory?
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Theory explains both positive and negative symptoms of schizophrenia. Testable evidence as people given a drug for Parkinson's disease by increasing dopamine production can experience hallucinations.
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What is the evidence from drug treatments?
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Many antipsychotic medications used to treat schizophrenia work by blocking dopamine
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How does Carlsson et al.(1999/2000) support this theory?
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Scanning shows that people with schizophrenia are more sensitive to excess dopamine than others.
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Weaknesses of this theory?
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Not all patients respond the antipsychotic drugs. The theory can't prove that excess dopamine causes schizophrenia and rather it may be a symptom. Reductionist.
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What did Alpert and Friedhoff (1980) find?
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Some patients didn't improve at all after taking dopamine antagonists
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What did Zipursky et al (2007) find?
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A review article found that blocking dopamine receptors does not always remove the symptoms inn patients who had schizophrenia for 10 years or more, even if the block is 90% effective.
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What did Brown and Birley (1968) find?
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50% of schizophrenic patients reported a major life event in the 3 weeks prior to relapse, highlighting social factors.
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What is another biological explanation for schizophrenia?
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Genetics
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What did Hilker et al (2018) find?
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There is a 79% heritability rate for schizophrenia.
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How does DiGeorge syndrome explain schizophrenia through genetics?
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Genes may mutate due to environmental factors or an error in cell division. DiGeorge syndrome occurs when 30-40 neighbouring genes are deleted. As many as 25% of people with this condition later develop schizophrenia.
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What did Wright (2014) suggest?
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As many as 700 genes have been linked to schizophrenia and the number continues to grow.
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What specific genes have been associated to schizophrenia?
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The COMT gene and the DISC1 gene
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How does the COMT gene link to schizophrenia?
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The deletion of the COMT gene from the DiGeorge syndrome leads to high levels of dopamine as COMT regulates dopamine levels
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What does DISC1 stand for?
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The Disrupted-in-Schizophrenia 1
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How does the DISC1 gene link to schizophrenia?
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People with an abnormality in this gene are 1.4 times more likely to develop schizophrenia (Kim et al, 2012).
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What does the DISC1 gene code?
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The creation of GABA, which regulates other neurotransmitters such as glutamate and dopamine in the limbic system
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What did Gottesman and Shields (1966) find?
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Concordance rates for severe schizophrenia was much higher in MZ twins (75%) than DZ twins (22%).
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What did Gottesman and Shields (1966) conclude?
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Schizophrenia does have a biological basis as the chance to develop schizophrenia is influenced genetically
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Strengths of this explanation?
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Supporting evidence, scientifically credible and has useful applications with genetic councelling
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Weaknesses of this explanation?
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Twin studies have flawed methodologies as MZ twins may be treated more similarly than DZ twins and this may not actually explain schizophrenia. Wright (2014) highlights confusion to which genes a responsible for Schizophrenia. Reductionist
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