The way
the Japanese and Koreans believe blood types are correlated with personality is pseudoscience. They believe that A types have what they call a "farmer's personality", with traits such as earnestness, reserve, patience, caution, stubbornness and pessimism. They call O types "hunter types" who supposedly would be confident, self-centred, ambitious, strong-willed, aggressive, intuitive, agreeable, competitive and athletic. Many scientific studies have looked into such assertions and none supported any correlation. This is particularly sad because the many Japanese earnestly believe in those pseudo-theories, and, according to
this Guardian article, this national obsession with blood type temperaments has been blamed for bullying of children in playgrounds, loss of job opportunities, and ending of happy relationships. Here is an excerpt:
"Blood typology has filled countless pages and a large chunk of television airtime since journalist Masahiko Nomi wrote the first of 30 hugely popular books on the subject in the early 1970s.
Daytime TV shows offer "blood horoscopes", while on sale are all manner of items supposedly tailored to each of the four blood groups, anything from chewing gum to condoms to bath salts - a relaxing, blue concoction for the sensitive type A.
Companies have been known to appoint employees to jobs based on their blood type, while dating agencies rank this genetic nugget alongside education and salary in recommending a male suitor."
Nevertheless, some scientific studies taking a different approach have shown that a certain degree of correlation might exist between personality and blood types in some populations because of two indirect factors:
1)
Tsuchimine et al. (2015) found that the dopamine beta-hydroxylase (DBH) gene is in linkage with the ABO gene. Using the Big Five Personality traits, they found a possible association between ABO blood group genotype and the Persistence trait, although it was relatively weak. Here is what they say:
"Personality trait research has found that low-activity DBH is associated with the impulsiveness trait, whereas high-activity DBH is associated with sensation seeking. The ABO group B marker rs8176746 and the low-activity DBH allele rs1611115T exhibit similar frequency distributions among HapMap populations. For these reasons, and considering the known effects of catecholamine on behavior, Hobgood suggested that linkage between DBH and ABO may explain the associations between personality traits and ABO blood type."
Their conclusion was:
"A post hoc analysis showed that the blood type A group had higher Persistence scores than the B and O groups (p = 0.009 and p = 0.018, respectively; Bonferroni correction)."
2) Blood types influence health risks for certain diseases. Here is their input.
"There are several lines of evidence that ABO blood type is associated with various diseases, including cardiovascular disease, cancer, and stress response-related immune disease. There are also reports that specific personality traits, such as depression and anxiety, may be associated with these diseases. Therefore, it is possible that ABO blood type is also associated with personality traits.
We evaluated two SNPs, rs8176719 and rs8176746, as markers of the ABO genotype in this study. The rs8176719 SNP indicates O-allele-specific 261delG, and the rs8176746 SNP determines the galactose specificity of the encoded A/B transferases and, thus, the expression of A and B antigens on erythrocytes. Many previous studies examining these two SNPs have reported associations between ABO blood type and various diseases, including the ‘blood type diet’, cardiometabolic risk, susceptibility to severe Plasmodium falciparum malaria, and pancreatic cancer."
However they do not investigate further this second hypothesis.
