Lack of sleep needs to be treated as a major health issue, according to a report published by the U.K. Mental Health Foundation. The report, Sleep Matters, suggests a link between insomnia and poor relationships, low energy levels and an inability to concentrate. Poor sleep has already been linked to depression, immune deficiency and heart disease. The report calls for G.P.s to have more training to recognise the symptoms. The number of adults suffering from insomnia in the U.K. has previously been estimated at around 30%. It showed people with insomnia were four times as likely to have relationship problems.