Smartphone usage at night can tires you out the next day, study says A smartphone "hangover" plaguing people that check their smartphones after 9:00 p.m. revealed users tend to be more exhausted the next day, according to a new study from Michigan State University. The drop in energy and productivity level is similar to a drinking hangover suffered the morning after partaking too much at the local pub. "It can be a double-edged sword," said Russell Johnson, MSU assistant professor of management, in a statement. "The night-time use of smartphones appears to have both psychological and physiological effects on people's ability to sleep and on sleep's essential recovery functions." I guess it won't stop people falling over from unchecked smartphone usage. Amongst the most annoying is when they do it in meetings.