Schizophrenia Genetic Risk — MRCPsych Paper B MCQ
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Correct answer: D — 10%
The correct answer is D, approximately 10%. Family studies show that the lifetime or morbid risk of schizophrenia in first-degree relatives of an affected person is around 10%; one directly relevant study estimated 10.9%. This is substantially higher than the general-population risk of approximately 1%, so A ignores the effect of family history. A risk of 20% is higher than the conventional estimate for one unspecified affected first-degree relative. Values around 40–50% are closer to reported concordance estimates for monozygotic twins and should not be applied to first-degree relatives generally. Exact estimates vary with the particular relationship, population and ascertainment method. Schizophrenia is polygenic and multifactorial, so family history increases susceptibility but does not make the disorder inevitable.
Reference: Onu JU et al. Morbid risk of schizophrenia amongst relatives of schizophrenia probands: A family-controlled study. South African Journal of Psychiatry. 2018. https://pubmed.ncbi.nlm.nih.gov/30568840/