Blood type is one of the body’s more mysterious taxonomies. There are four bins our blood can fall into — A, B, AB, and O — and together they represent the four groups of antigens found on the surfaces of red blood cells. But they don’ t just signal who we can donate to and receive from; our blood types can reveal complex patterns of personal health. Here are six to consider:

1. Memory Problems

At-risk: AB

Your brain and vascular system have more in common than you may think. A recent study found people with type AB blood were 82 percent more likely to experience difficulties with memory recall, language, and attention than people with other types. One reason, researchers suspect, is due to the key clotting protein, known as coagulation factor VIII, which may actually reduce the quality of blood flow to the brain, rather than sealing up injury sites.

“Since factor VIII levels are closely linked to blood type, this may be one causal connection between blood type and cognitive impairment,” said Mary Cushman, author of the recent study, to Yahoo Health.

2. Pancreatic Cancer

At-risk: Non-O

It may be more accurate to say people with type O blood are at a lower risk for pancreatic cancer, given the work researchers from Yale University are doing on bacterial infection. In a study conducted last July, scientists from the University’s Cancer Center looked at cases of a common species of bacteria called Helicobacter pylori, or H. pylori, that lives in people’s gut.

They found people with H. pylori were significantly more likely to develop pancreatic cancer, due to the way A and B antigens help the bacteria thrive. People with type O blood carry no antigens on the surface of their red blood cells. This is what allows them to donate to anyone.

3. Heart Disease

At-risk: AB

A 2012 study from Harvard University found people with non-O blood also happen to have an increased risk for cardiovascular disease. But those with type AB blood were the most at-risk overall, demonstrating a 23 percent greater chance of suffering from heart disease than type O subjects.

Study author Dr. Lu Qi, an assistant professor in the Department of Nutrition, said the particular makeup of people’s antigens should be given the same weight we already assign to cholesterol and blood pressure. "While people cannot change their blood type, our findings may help physicians better understand who is at risk for developing heart disease,” Qi said in a statement.

4. Stress

At-risk: A

Because certain blood types are more likely to co-occur with varying levels of hormones in the body, physicians commonly tailor their exercise recommendations to the patient’s type. People with type A blood, for example, are more likely to have higher levels of cortisol, the stress hormone, in their body. So, stress-reducing exercises, like Tai Chi and yoga, may be more beneficial at cutting that tension than running or weightlifting alone.

When the adrenal gland dumps more and more cortisol into the blood, people’s stress response grows more acute. People with type A blood may find themselves getting anxious more quickly and having a harder time letting troubles roll off their back.

5. Exercise Demands

More generally, the makeup of a person’s antigens on his or her red blood cells can determine how much of a certain hormone gets released. People with type A and B blood respond better to calming, low-intensity exercise like yoga, especially if depression runs in the family. Likewise, people with AB blood benefit from well-rounded workouts that keep their immune systems in check. Type O people, however, are a different story.

“Type O’s are more prone to problems that arise from an inability to clear stress hormones from their system quickly,” Dr. Ginger Nash, a naturopathic physician, told Personalized Living. “It takes more to get a Type O stressed but it takes more to de-stress them as well.”

6. Gut Bacteria

In addition to living on your red blood cells, antigens are often found in the lining of your digestive tract — about 80 percent of people fall into this category. Much of the bacteria living in people’s gut uses these antigens as food, which largely determines which bacteria flourish and which disappear. Prior research has estimated, for instance, that people with type B blood contain up to 50,000 times the number of strains of friendly bacteria than people with either type A or O blood.

“Increasingly, studies are showing that changes in the microflora content of the digestive tract can be linked to metabolic illnesses, including type II (adult onset) diabetes and obesity,” wrote Dr. Peter D’Adamo, physician and author of Eat Right 4 Your Type, in a blog post. “Blood group and secretor status play an important role in conditioning the overall characteristics of the digestive tract.”