"...Our results are not in favor of a direct involvement of the HLA system in development of schizophrenia, but are compatible with the possible existence of a susceptibility gene in the MHC region at chromosome 6p 21.31."
*Schwab SG et al., Am J Med Genet. 2002 Apr 8;114(3):315-20. Investigation of linkage and association/linkage disequilibrium of HLA A-, DQA1-, DQB1-, and DRB1-alleles in 69 sib-pair- and 89 trio-families with schizophrenia.
In addition, here is another paper** from Saudi Arabia -- probably including non-sanguine subjects with schizophrenia -- that similarly queries whether HLA association with schizophrenia is due to an unidentified linked gene:
”…However it is not clear whether the DRB1*03 alleles have a direct causal role in the etiology of schizophrenia or if they are in direct linkage disequilibrium with another true susceptibility locus.”
** Kadasah S., et al., Journal International Journal of Psychiatry in Clinical Practice, Vol. 15, 2011. ,HLA-DRB1 association with schizophrenia in Saudi Arabian patients.
So, it seems that the HLA issue -- of a major gene possibly affecting behavior on chromosome 6 in linkage disequilibrium with the MHC genes -- is a hypothesis that has indeed been put forward in the research literature. However, during the past decade, no one has taken the ball and run with it… probably because of the conventional wisdom that “no single gene influences any aspect of behaviour by more than a few percent.”
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