Thanks to the clocks going back, many of us managed to grab a little bit of extra shut-eye over the weekend. And that’s no bad thing because, as a country, we seem to be chronically sleep-deprived. According to the Sleep Council, the average Briton gets six-and-a-half hours sleep a night, which for most people is not enough. Lots of studies have shown that cutting back on sleep, deliberately or otherwise, can have a serious impact on our bodies. A few nights of bad sleep can really mess with our blood sugar control and encourage us to overeat. It even messes with our DNA. A few years ago, Trust Me I’m a Doctor did an experiment with Surrey University, asking volunteers to cut down on their sleep by an hour a night for a week. Dr Simon Archer, who helped run the experiment, found that getting an hour’s less sleep a night affected the activity of a wide range of our volunteers’ genes (around 500 in all) including some which are associated with inflammation and diabetes. Disturbed nights So the negative effects on our bodies of sleep deprivation are clear. But what effect does lack of sleep have on our mental health? To find out Trust Me teamed up with sleep scientists at the University of Oxford to run a small experiment. This time, we recruited four volunteers who normally sleep soundly. We fitted them with devices to accurately monitor their sleep and then, for the first three nights of our study, let them get a full, undisturbed eight hours. For the next three nights, however, we restricted their sleep to just four hours. Each day our volunteers filled in a psychological questionnaire designed to reveal any changes in their mood or emotions. They also kept video diaries. So what happened? Sarah Reeve, a doctoral student who ran the experiment for us was surprised by how quickly their mood changed. “There were increases in anxiety, depression and stress, also increases in paranoia and feelings of mistrust about other people”, she said. “Given that this happened after only three nights of sleep deprivation, that is pretty impressive.” Three of our four volunteers found the experience unpleasant, but one of them – Josh – claimed to be largely unaffected. “This week probably hasn’t taken as much of a toll as I thought it would on me,” he said. “I feel perfectly fine – not happy, sad, stressed or anything.” Yet the tests we did on him showed something very different. His positive emotions fell sharply after two nights of disturbed sleep, while negative emotions began to rise. So even though he felt OK there were signs that he was, mentally, beginning to suffer.