Modified DA Hypothesis — MRCPsych Paper B MCQ

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ModerateSchizophrenia & PsychosisModified DA HypothesisMRCPsych Paper B

According to the Davis et al. modified (version II) dopamine hypothesis of schizophrenia, which pattern of dopaminergic dysfunction was proposed to account for the coexistence of positive and deficit symptoms?

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Correct answer: B — Mesolimbic hyperdopaminergia with mesocortical hypodopaminergia

Explanation lettering: C = shown as A · A = shown as C · E = shown as D · D = shown as E

The correct answer is B. Davis et al.'s modified dopamine hypothesis proposed reduced dopamine activity in the prefrontal mesocortical system, associated particularly with deficit or negative symptoms, alongside excessive mesolimbic dopamine activity associated with positive psychotic symptoms. This replaced the earlier, overly simple concept of global dopaminergic excess. A omits the cortical component, while C reverses the proposed abnormalities. D describes pathways principally relevant to antipsychotic extrapyramidal and prolactin-related adverse effects rather than the proposed pathophysiology of schizophrenia. E cannot account for the hypothesised dopaminergic contribution to positive symptoms. Later models place greater emphasis on presynaptic striatal dopamine dysregulation and upstream biopsychosocial risk factors, but this does not alter what the named Davis version II hypothesis proposed.

Reference: Howes OD, Kapur S. The dopamine hypothesis of schizophrenia: version III—the final common pathway. Section describing version II. Schizophrenia Bulletin. 2009;35(3):549–562. https://pubmed.ncbi.nlm.nih.gov/19325164/