Exasperated parents have been trying to find an explanation for teenage moods for decades.

Now US researchers say adolescent angst could be down to excessive levels of nerve activity in the brain.

They say this is so intense, teenagers find it hard to process basic information, leaving them socially and emotionally inept.

And the nerve activity manifests itself in the stereotypical surly, snappy moods and teen temper tantrums.

Tests, reported in New Scientist magazine, showed that teenagers’ emotional radar seems to switch of at around 11, and is not back up to full strength until the teenagers reach 18.

Three hundred people aged between 10 and 22 were asked to judge emotions expressed in images and words.

It was found that by the age of 11 the speed at which people could identify emotions such as anger or happiness dropped by up to 20%.

But it gradually improved each year and returned to normal at 18.

‘Remodelling’

Past research has shown that when children hit puberty, there is a sudden increase in connections between nerves in the brain, particularly in the prefrontal cortex

Robert McGivern, of San Diego State University, who led the study which is also published in the journal Brain and Cognition, said: “This plays an important role in the assessment of social relationships, as well as planning and control of our social behaviour.”

He said teenagers’ brains were experiencing a temporary “remodelling” of the brain at exactly the period where they were being exposed to a greater variety of social situations.

This can lead to them finding emotional situations more confusing, leading to typical teenage petulance.

‘Avoid face-offs’

But Dr Anne McPherson, an Oxfordshire GP who specialises in teenage health told BBC News Online: “We don’t know if this is the answer, and it’s all down to some action in the brain. We need much more research.”

She added: “Teenagers do get mood changes to do with puberty, but we need more information about how the brain is affected.”

Dr McPherson said the important thing was for parents to know how to deal with teenage tantrums.

“Avoid face-offs, but don’t be afraid to say what they think in terms of giving guidelines and making limitations to how they should behave.”