Which blood type is most likely associated with depression?

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.

See the study:

https://www.sciencedirect.com/science/article/pii/S2666144623000163

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