Teenagers are more vulnerable to drug abuse and mood disorders because their brains function differently when they are enjoying themselves, scientists have suggested.

A study of rats found more neurons were activated in adolescents' brains when they received tasty treats than those of adults - meaning they over-processed rewards and became vulnerable to addictive or impulsive behaviour.

This could explain why youngsters take more risks and tend to develop disorders like addiction, depression and schizophrenia, the Daily Express reported.

"Adolescents often respond differently than adults to ... peer interactions and pleasurable stimuli," said Professor Bita Moghaddam, with doctoral student David Sturman of Pittsburgh University in the US.

They said that recognising the difference in brain processes of adolescents was critical to understanding this phenomenon, as well as their behavioural and psychiatric problems, such as drug abuse and mood disorders.