Everyone’s done the blood sugar dance at some point: For some unexplainable reason, you get into a bad mood and maybe take it out on the person next to you or the driver of the car in front of you. Later, when you have a little snack, your mood seems to reverse itself.

A new study looks into this phenomenon, familiar to dieters and the parents of young children, and finds that when blood sugar levels drop, even happily married people become more likely to report being angry at their spouses.

The same people who’d jabbed more pins into the voodoo dolls in the first experiment were more likely to deliver the longest and loudest noise blasts in the second experiment.

No spouses were harmed in this experiment, but some clever methods were used to get at spousal anger. Over 100 married couples measured their blood sugar once in the morning and once at night.

Researchers gave each person a voodoo doll representing their spouse and 51 pins. Each participant was instructed to (privately) indicate their anger level at their spouse by jabbing as many pins as they wanted into the doll each evening. As you might guess, when blood sugar was low, the voodoo dolls received more pin pokes.

“When they had lower blood glucose, they felt angrier and took it out on the dolls representing their spouse,” study author Brad Bushman said in a news release. He and his team even coined a new term for the hungry/angry combination: “Hangry.”

“We found that being hangry can affect our behavior in a bad way, even in our most intimate relationships,” said Bushman, a professor of communication and psychology at The Ohio State University.

And even couples who reported having the strongest relationships exhibited the low blood sugar-anger connection.

In the second part of the experiment, couples came to the lab and competed with each other to see who could hit a button fastest when they saw a square on a computer screen turn red. The “winner” could then send a blast of noise — as long and loud as they wanted — into the room where their spouse was.

In reality, they weren’t playing against each other. They were playing against a computer who let them win half the time. And the spouses in the other room weren’t really getting the blast the player thought he or she was delivering.

“Within the ethical limits of the lab, we gave these participants a weapon that they could use to blast their spouse with unpleasant noise,” Bushman said.

People with lower blood sugar levels sent (or thought they were sending) the loudest blasts to their spouses — even those in the most satisfying relationships. The same people who’d jabbed more pins into the voodoo dolls in the first experiment were more likely to deliver the longest and loudest noise blasts in the second experiment.

Tips for Better Couple Communication

The findings make perfect sense when you consider that the brain uses a lot of fuel during the course of a day. Though the brain only makes up about 2% of our body weight, Bushman points out, it consumers about 20% of the body’s glucose reserves.

When glucose is low, the areas of the brain responsible for self-control —and for dealing with anger in appropriate ways — aren’t able to do their job as well.

The bottom line is to keep your blood sugar as stable as possible. It helps to eat smaller meals throughout the day and try to stick to foods lower on the glycemic index, so your blood sugar doesn’t spike and then crash.

Bushman recommends that couples have a bite to eat before any important talk. “It's simple advice but it works: Before you have a difficult conversation with your spouse, make sure you're not hungry.”

The study is published in Proceedings of the National Academy of Science.