Modified Dopamine Hypothesis — MRCPsych Paper B MCQ
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Correct answer: B — Subcortical hyperdopaminergia with prefrontal hypodopaminergia
The correct answer is B. The version II, or modified, dopamine hypothesis proposes regional rather than generalised dopaminergic dysfunction: excessive subcortical, classically mesolimbic, dopamine activity is associated with positive psychotic symptoms, while reduced prefrontal or mesocortical dopamine activity is associated with deficit and cognitive symptoms. Option C omits the cortical deficit, whereas C reverses the proposed pattern. Option A reflects the earlier, overly broad hyperdopaminergia hypothesis. Option D is incompatible with a dopamine hypothesis, although serotonergic and other neurotransmitter systems may contribute to schizophrenia. Later version III models further refined this account by emphasising increased presynaptic striatal dopamine function as a final common pathway linking biological and psychosocial risk factors to psychosis.
Reference: Howes OD, Kapur S. The dopamine hypothesis of schizophrenia: version III—the final common pathway. Schizophrenia Bulletin. 2009;35(3):549–562. https://pubmed.ncbi.nlm.nih.gov/19325164/