When children are deprived of sleep it may not be obvious as they may not appear tired. Instead it may show up in their behaviour. A new study by researchers from the University of Helsinki and the National Institute of Health and Welfare in Finland studied the link between children's sleep patterns and their subsequent behaviour. Those children who slept on average less than 7.7 hours a night were shown to have a higher score for hyperactivity and impulsive behaviour. None of the children had ADHD yet they were displaying ADHD symptoms. Although the ideal is 8 hours of sleep a night, the researchers acknowledge this varies from individual to individual and suggest parents look our for behavioural changes in their children as an indication they are not getting enough sleep. 280 healthy children took part in the study.