The term 'hangry', a combination of hunger and anger, has been a part of the common lexicon for a while. Now there is some scientific basis behind the term, according to a new study involving 64 adult participants from Europe.

Over the course of 21 days, the volunteers were asked to record their emotions and hunger pangs five times a day via a smartphone app. What the researchers found was that hunger is associated with a higher level of anger and irritability, and fewer pleasurable feelings.

These links were significant even after differences in age, sex, body mass index, dietary behavior and personality traits were all factored in. In other words, how well fed we are seems to have a notable influence on our feelings of anger.

"Many of us are aware that being hungry can influence our emotions, but surprisingly little scientific research has focused on being 'hangry'," says social psychologist Viren Swami, from Anglia Ruskin University in the UK.

"Ours is the first study to examine being 'hangry' outside of a lab. By following people in their day-to-day lives, we found that hunger was related to levels of anger, irritability, and pleasure."

Across a total of 9,142 data points submitted by those taking part in the study, hunger was associated with 48 percent of the variance in anger, 56 percent of the variance in irritability, and 44 percent of the variance in pleasure.

The researchers also found that the negative emotions could be linked to eating patterns averaged out over several days, as well as individual day-to-day variations. 'Hanger' is something that can persist over time.

While the study relied on subjective reports given by the participants in regards to how hungry they felt at specific times, it's still what the team calls a "robust" link between hunger and anger.

"The results provide a high degree of generalizability compared to laboratory studies, giving us a much more complete picture of how people experience the emotional outcomes of hunger in their everyday lives," says psychologist Stefan Stieger, from the Karl Landsteiner University of Health Sciences in Austria.

The same sort of 'hangry' behavior has been seen elsewhere in the animal kingdom too, and scientists are hard at work trying to understand the cues from biology, personality and our environment that might be behind the association.

Previous studies have suggested a lower blood glucose level might be something to do with our tendency to get 'hangry', but as yet there have been no definitive conclusions about why hunger leads to anger and irritability in this way.

Knowing more about how these feelings and emotions develop in relation to the contents of our stomach can ultimately help us manage them better, the team suggests – even if it's just a case of recognizing what's happening within our own bodies.

"Although our study doesn't present ways to mitigate negative hunger-induced emotions, research suggests that being able to label an emotion can help people to regulate it, such as by recognising that we feel angry simply because we are hungry," says Swami.

"Therefore, greater awareness of being 'hangry' could reduce the likelihood that hunger results in negative emotions and behaviors in individuals."

The research has been published in PLOS One.