Enough sleep has a number of benefits including rejuvenation of body cells, clearer thinking, less depression https://sleepfoundation.org/press-release/national-sleep-foundation-recommends-new-sleep-times/page/0/1 accessed15 August 2017

Not enough sleep can lead to a number of problems, these can include physically experiencing tiredness or hypertension, mentally having difficulty concentrating and completing cognitive tasks, being more likely to have an accident, less able to cope with stress, less able to regulate emotions, and reduced immune system function. http://www.euro.who.int/__data/assets/pdf_file/0008/114101/E84683.pdfaccessed 17 August 2017