Adene Sanchez via Getty Images Sleeping more than nine or 10 hours a night is linked to certain health risks like depression and diabetes. But experts aren’t sure if oversleeping causes these issues or if it’s a sign of an underlying condition. For years, we’ve been told how detrimental a lack of sleep can be for our mental and physical health. (Think: weakened immune function, low mood and impaired cognitive performance, while also putting you at increased risk for more serious issues like heart disease and diabetes down the road.) But is it bad to get too much sleep — and if so, how much is too much?