Blood Types among ADHDers

Stuff you should know about blood types

There are only four possible blood types: A, B, AB, and O
Blood types are either positive or negative. This is called the Rhesus factor.
Blood types (A, B, AB, O) are hereditary, as is the Rhesus factor (+, -).
- In other words, if both of your biological parents have a negative blood type, you will too.
- Your type (letter) depends on your parents' blood type alleles.
There are three alleles: A, B, and O. A and B are both dominant. O is recessive.
Everyone has two alleles for their blood type.
- You can have two different ones (heterozygous) or two that are the same (homozygous).
- You can only have type O blood if you received an O allele from both parents. In this case, you would have two O alleles.
  - It's possible to have an O allele without having type O. For example, if you have one A and one O allele, you have type A blood.
Offspring won't always have the same exact blood type as their parents ... unless both parents have type O.
If you have type AB, then you received an A allele from one parent and a B allele from another.

About this survey data

I was curious if people with ADHD were more likely to have a specific blood type. After falling down a Google rabbit hole, I found a 2009 study on this exact topic. Researchers found that ADHD is more commonly associated with A and O alleles than B . In other words, people with blood types A or O may be more likely to have ADHD than those with type B.

Before you look at the results, I want to clarify something: I did not test respondents' alleles. I only recorded blood types as they were reported to me. My point? This data isn't conclusive because it's impossible to know if the type A and B respondents were heterozygous (2 different alleles: AO, BO) or homozygous (AA, BB). So, don't take anything on this page as hard science — I'm just sharing because it's interesting! 🤓

This survey was conducted in 2021.

Note: extreme difference in cohort sample size may not accurately represent the whole population.

SOURCE:

Guo XS, Jiao BQ, Xu T. (2009). Correlation between ABO blood type gene and attention-deficit hyperactivity disorder in children. Chinese Journal of Contemporary Pediatrics, 11(5): 371-373.

Survey Participant Demographics

Total number of participants: 362

ADHD participants: 337

Diagnosed with ADHD: 225
Undiagnosed but strongly suspect ADHD: 112

Non-ADHD participants: 25

Control group (7%)

Figure 1

Figure 1: Blood Type Prevalence in ADHD vs. Non-ADHD Groups. Of 362 total participants, distribution of self-reported blood types were 33.4%, 13%, 5.3%, and 48.3% for blood types A, B, AB, and O, respectively. For the ADHD group, type O was the most common at 49.3%, compared to 36% for the non-ADHD group. Type B was more common in non-ADHDers than in the ADHD group, at 20% and 12.5%, respectively.

Figure 2

Blood type and rhesus factor prevalence in adhd vs non-adhd groups.png

Figure 2: Blood Type & Rhesus Factor Prevalence in ADHD vs. Non-ADHD Groups. (The same as blood types in figure 1, but with the rhesus factor - positives and negatives - included.) Of 362 participants, O+ was the most common blood type at 32.04%, followed by A+ (26.24%) and O- (16.3%). The rarest type among respondents was AB- (1.1%). Comparing the ADHD vs. non-ADHD groups, the rate of negative types was consistently higher than corresponding positive types. For A, B, AB, and O types in ADHDers, negative variants were 3.9x, 5x, 3.3x, and 2.1x more prevalent than their positive variants, respectively. For A and B types in non-ADHDers, negative variants were only 2x and 4x more prevalent than their positive variants, respectively. In the non-ADHD group, more people had O+ than O-. Lastly, given that zero non-ADHD participants had AB+, AB variants could not be calculated for comparison.

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