WASHINGTON—Aggressive behavior toward a spouse may be caused by low blood sugar levels, according to a study published online in Proceedings of the National Academy of Sciences.
Taking over three years to carry out, the study was completed in several phases with the participation of 107 married couples. At the end of the study, researchers found that blood glucose level was an accurate predictor of how angry an individual would be with their spouse.
Scientists concluded that hunger brought about by low blood glucose levels may be a factor in marital arguments and perhaps even some domestic violence situations.
“People can relate to this idea that when they get hungry, they get cranky,” said Brad Bushman, lead author of the study and professor of communication and psychology at The Ohio State University. Bushman explains that the phenomenon is so common that there is even a slang term for it: hungry +angry = “hangry.”
“We found that being hangry can affect our behavior in a bad way, even in our most intimate relationships,” he said.
At the beginning of the study the participants completed a relationship satisfaction measure, which assessed how happy and fulfilled each individual felt in their marriage.
The first part of the study consisted of a 21-day period during which participants’ blood glucose levels were measured every morning and night. Subjects were also given a voodoo doll that represented their spouse, along with 51 pins and asked to insert 0 to 51 pins into the doll at the end of each day, representing how angry they felt with their spouse. The participants did this out of the presence of their spouse and recorded the number of pins they stuck in the dolls every night for the 21-day period.
The preliminary findings at this stage were that, even after adjusting for each couple’s relationship satisfaction, the lower an individual’s evening blood glucose, the more pins they stuck in the voodoo doll.
“When they had lower blood glucose, they felt angrier and took it out on the dolls representing their spouse,” said Bushman. “Even those who reported they had good relationships with their spouses were more likely to express anger if their blood glucose levels were lower.”
The next part of the study involved couples taking part in an experimental task where they were told they would compete with their spouse in a computer game. They were also told that the winner could blast their spouse, who would be in a separate room, with a loud noise.
Individuals were in reality competing against a computer that let them win about half the time and their partners were not really blasted with noise when they lost. However, participants were allowed to pick how loud and how long the blast to their partner would be when they “won.”
The results showed that people with blood glucose levels that were lower than average chose louder and longer sound blasts for their spouse. The results remained even when researchers accounted for differences between men and women and relationship satisfaction.
Researchers also noted that those who delivered longer and louder sound blasts also stuck the most pins into the voodoo doll representing their spouse.
“We found a clear link between aggressive impulses as seen with the dolls and actual aggressive behavior,” said Bushman.
Bushman explains that it takes energy for the brain to exert self-control over anger and aggressive impulses. Since that energy is provided in part by glucose, when glucose levels are low, the brain is not as effective in controlling irritation and violent behavior.
“Even though the brain is only 2 percent of our body weight, it consumes about 20 percent of our calories. It is a very demanding organ when it comes to energy,” he said.
“It’s simple advice but it works: Before you have a difficult conversation with your spouse, make sure you’re not hungry.”