Blood group and personality type: myth busters

Profile on @Quora for Asher Nitin, Physician, artist, athlete, student of Christian theology.

When I looked at the answers to this question, I was surprised to find people writing about how blood groups determine a person’s personality. I now find myself forced to answer this question because whoever created this question tagged it under scientific research. So I’m going to answer this using scientific research.

The blood typing systems that pseudoscience proposes can be used to type people into various personalities are the ABO system and Rh system. These systems use markers on the surface of RBCs to determine blood type.

These is an RBC (red blood cell).

This is the surface of the red blood cell via an electron microscope.

Chemically, this is what the surface looks like.

It comes down to basically carbon, hydrogen, oxygen and nitrogen atoms.

Now, embedded within this surface are the protein markers that determine blood type. Proteins are basically folded chains of amino acids. Amino acids are mostly made of C, H, O, N and S. These protein markers determine how RBCs of one person’s blood will interact with the serum of another person’s blood.

Now, this is the human brain.

You see that thin clingy film around it? That’s part of three physical barriers that wrap around the brain. And there are chemical barriers too.

In fact, there are three organs here:
the blood,
the cerebrospinal fluid (CSF)
and the brain.

So this area has three chemical barriers:
a blood-brain barrier,
a blood-CSF barrier,
and a brain-CSF barrier.

One of the effects of this intricate multilayered physical and chemical barrier is this: red blood cells never touch the neurons in the brain! Never. So it is impossible for RBCs to physically influence neural traits.

What about genetics then? What if the same genes that code for blood groups also code for personalities?

They don’t. We know the exact location of the genes that code for blood groups on the human genome. And we know the exact location of some of the genes that code for human personality. But more importantly, genes are not the only determinant of personality. They are not even the primary determinant of personality. They place a slightly bigger role in some rare conditions like psychosis or mania, but that’s it.

A person’s personality is affected by his IQ, EQ, dietary deficiencies, embryological development, early childhood experiences, cultural cues, religious beliefs, chemicals ingested (alcohol, caffeine, ecstasy, PCP), physical contact, atmospheric oxygen content, traumatic brain injury and more.

We take all these into account in neurology and psychiatry. Believe me, if blood groups were relevant, we would use this information. We don’t.

A person’s blood group has close to zero relevance to his personality and mindset. Most of this superstition arose the same way astrology arises: confirmation bias, self-fulfillment and lack of statistical analysis.

The proof lies in the links people will attach to prove the blood group personality theory. They will all be links to naturopathic or independent websites.

Just because a website says something doesn’t mean it’s true. On the other hand, if it was a link to a medical website (scientific medicine) citing a randomized double-blind study, then it might be real science.

But none of those links will ever direct you to anything with verifiable data. Just claims and talk of studies. And numbers that will look like data.

Additional point: as Raghuraj S. Hegde pointed out in the comments section below, RBCs undergo enucleation early in their life. That is to say, they discard their nucleus. The nucleus holds all the genetic material that is transmitted. So it is simply impossible for them to carry are the similarities of people having the same blood group? 

~by Asher Nitin


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