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Forgiveness, Resentment and Blood Sugar?

New research links diabetic symptoms with a reduced likelihood of forgiving others.
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By now, we’ve all been alerted to the warning signs of diabetes. Frequent urination. Unquenchable thirst. Tingling in the hands and feet.

And, of course, a tendency to hold a grudge.

Writing in the journal Personality and Individual Differences, a research team led by University of Kentucky social psychologist C. Nathan DeWall links symptoms of Type-2 diabetes to lower levels of forgiveness. Their study suggests low levels of blood glucose are not only dangerous to your health: They may also be poisonous to your personality.

DeWall and his associates describe four experiments testing their thesis, three of which featured 511 volunteers (average age 28) who participated in an Internet survey. They first completed the revised Diabetic Symptoms Checklist, which measures the number and severity of a variety of diabetes symptoms. (Examples include “Numbness or loss of sensation in the feet” and “Shortness of breath at night.”)

Their willingness to forgive was then measured using three different scales. First, they filled out a 10-item survey measuring the degree to which they are predisposed to pardon. It featured questions such as “I can forgive a friend for almost anything.”

Second, they reported their likely forgiveness level in five hypothetical scenarios, such as “Would you forgive a person who revealed something you told them in confidence?” Third, they reported to what degree they had actually forgiven someone who recently hurt them.

The researchers found a positive correlation between diabetic symptoms and a tendency to be unforgiving in both the real and hypothetical situations. They also found a negative correlation between the symptoms and one’s general tendency to forgive.

For the fourth and final study, participants (182 volunteers) played a computer game in which they could respond to their partner’s negative behavior by either forgiving them and moving on, or by retaliating and becoming uncooperative themselves. “As expected, diabetic symptoms correlated negatively with cooperative behavior,” they write.

While conceding their findings measure correlation rather than causation, DeWall and his colleagues point to low blood glucose levels as the likely trigger for these resentful attitudes.

“Glucose is fuel for the brain,” they write. “All brain activities require at least some glucose, but tasks that require self-control require large quantities of glucose.” As we’ve previously reported, self-control appears to be a limited resource; DeWall notes it is also “a crucial factor in promoting forgiveness,” in that it inhibits “potentially destructive impulses.”

People with Type-2 diabetes have a reduced ability to efficiently process glucose, which presumably reduces their ability to exert self-control. This can lead to a negative spiral on a personal level — it’s harder to stay on a diet if your self-control mechanism is damaged — but this study suggests it also has negative ramifications in the social sphere.

We all know the diabetes rate is increasing, and many commentators have complained we’re becoming a less-cordial society. Is it possible these two trends are connected?