Association of ABO blood types with psychiatric disorders: Potential biomarkers of genetic susceptibility?

Background

Published reports have suggested associations between ABO blood type and various medical conditions such as duodenal ulcers or stomach carcinomas. Studies have also linked this blood type to preoperative anxiety, indicating a possible psychiatric connection. This prompted us to review the literature for possible associations between blood types and one or more psychiatric disorders in controlled studies.

Methods

Using search engines including PubMed and Google Scholar, we used the key words “ABO blood types”, “depression”, “anxiety”, “schizophrenia”, “bipolar disorder”, “dementia” and “psychiatric disorder” to collect published controlled studies on this topic.

Results

Eighteen reports were identified, which investigated the association between blood types and various psychiatric disorders. Some studies reported that the AB blood type was correlated with higher levels of anxiety and cognitive impairment. Another study found that individuals with bipolar or unipolar affective disorder had a higher prevalence of type O blood and a significantly lower rate of type A blood. However, patients with involutional depression were reported to have a higher rate of type A blood and significantly lower rate of type O. None of the blood types were found to have any significant association with risk for dementia, nor were there any significant differences in blood type between those with schizophrenia and healthy controls. Several studies also reported negative findings between blood type and the occurrence of different affective disorders.

Discussion

The studies in this review suggest a possible connection between ABO blood types and certain psychiatric disorders, as well as highlight the controversy in this field of research. How blood types predispose to some mental disorders has not been fully explored and warrants further investigation.