One in four 11 to 15-year-olds in England have too little sleep, a World Health Organization study suggests.
The Health Behaviour in School-aged Children report questions 3,398 11, 13 and 15-year-olds every four years.
And 27% now say they are too tired to concentrate on their lessons – 17% of 11-year-olds, 28% of 13-year-olds and 42% of 15-year-olds.
The proportion of 15-year-olds who say they have have low moods at least once a week has also risen, from 40% to 50%.
One in four 15-year-olds say they have self-harmed – and the proportion is rising faster among boys.
Girls, though, are more likely to have too little sleep, 32% compared with 23% of boys.
Just one in six of the youngsters (15%) say they are physically active for at least an