When you next see red, don't snap at your colleagues or scream into a pillow — writing down your feelings, then shredding or throwing them away is an effective way to calm down, a Japanese study has found.

"We expected that our method would suppress anger to some extent," said Nobuyuki Kawai, lead author of the study published this week in the journal Scientific Reports. 

"However, we were amazed that anger was eliminated almost entirely," said Kawai, a cognitive science professor at Nagoya University.

Around 100 students took part in an experiment where they were asked to write brief opinions on social issues, such as whether smoking in public should be outlawed.

The researchers told them that a doctoral student at Nagoya University would evaluate their writing.

But regardless of what the participants wrote, the evaluators scored them low on intelligence, interest, friendliness, logic and rationality.

They also received insulting feedback, which said: "I cannot believe an educated person would think like this. I hope this person learns something while at university."

The students then wrote down their feelings, and half of them — "the disposal group" — shredded the paper or threw it away, while the other half — "the retention group" — put it in a clear folder or a transparent box.

All the participants "showed an increased subjective rating of anger" after being insulted, the study said.

But while the anger of the retention group remained high, "the subjective anger for the disposal group decreased" to the point of being neutralised.

The researchers argued that their findings could be used as a form of ad-hoc anger management.

"Controlling anger at home and in the workplace can reduce negative consequences in our jobs and personal lives," they said.