Scientists say that a 30 minute online training session can be used to reduce stress in teenagers.

A low-cost, effective treatment for adolescent stress has been suggested by a study involving more than 4,000 secondary school pupils and university undergraduates.

The approach focuses on seeing stress as an opportunity for growth and interpreting the effects of stress on the body.

The first author of the study said that they were trying to change teenagers' beliefs about stress. When your body starts to feel stressed, that could be a good thing.

Mental health problems are on the rise in UK teenagers, with rates of probable mental health disorders increasing from one in nine to one in six by the year 2021, and there are long waits for services in some parts of the country.

Sports and education psychology use the growth mindset concept. The new approach encourages people to see the physical signs of stress as beneficial, such as a pounding heart and increased oxygen flow to the brain.

The 30-minute intervention appeared to have powerful effects on stress, academic performance and mental health, according to a series of six randomized controlled trials.

In one trial, 166 students were given either the intervention or placebo to learn about the brain. They were surprised to be asked to give a speech about their strengths and weaknesses in front of peer evaluators who had been trained to create an unsupportive atmosphere. The people who had received the intervention had lower stress responses.

Students were more likely to pass class at the end of the academic year after the intervention was shown to influence academic achievement. Teenagers who did the training reported lower levels of anxiety several months later.

The approach went against the "pervasive ethic of self-care" that often appears to view stress as negatively and suggests people "go do yoga or have a camomile tea". It doesn't help you deal with the underlying cause of stress.

The findings are in a journal.