LONDON (Reuters) - Parents of teenagers can breathe a sigh of relief; scientists believe they have discovered the cause of teenage angst.

The good news is that the surly, snappy moods and temper tantrums are caused by a temporary increase in nerve activity in the brain that makes it difficult for adolescents to process information and read social situations.

The bad news is that it lasts until about 18 years old.

Robert McGivern and his team of neuroscientists at San Diego State University found that as children enter puberty, their ability to quickly recognize other people's emotion nosedives, New Scientist magazine reported Wednesday.

Research has shown that during puberty the connectivity of nerves in parts of the brain, particularly the prefrontal cortex, increases.

"This plays an important role in the assessment of social relationships, as well as planning and control of our social behavior," McGivern said.

When he and his colleagues tested the ability of people between the ages of 10 and 22 years to judge emotions expressed in images and words, they discovered it altered with age.

By age 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.

McGivern said the temporary "remodeling" of the brain occurs just when teens go through different social and emotional experiences.

"As a result, they can find emotional situations more confusing, leading to the petulant, huffy behavior adolescents are notorious for," according to the magazine.