Do you find it difficult to get a good night's sleep? If you do, you are not alone. According to the US National Institutes of Health, between 6 and 30 per cent of adults suffer from insomnia or lack of restorative sleep. Since the establishment of sleep medicine a century ago, we have learnt a lot about the causes of sleeplessness. And yet, as the continuing development of new sleep aids demonstrates, its prevalence remains high. Persistent lack of sleep can have serious consequences for your health but despite this some writers, and other creative people, seem to welcome it. Franz Kafka famously claimed that if he couldn't pursue his stories through the night, they would "break away and disappear". Iszi Lawrence discusses our changing understanding of insomnia, and its hold over our imagination, with Dr. Manvir Bhatia, the vice-president of Indian Society for Sleep Research; science journalist Kenneth Miller, author of Mapping the Darkness; the Scottish writer – and self-confessed ‘intermittent insomniac’ - A L Kennedy; and World Service listeners.(Photo: A woman lying awake on a bed at night. Credit: Pony Wang/Getty Images.)