Struggle to get out of your double bed on a Monday morning? Scientists have found a real excuse for us – social jet lag! Experts have found that having a lie-in at the weekend can cause us to be extremely tired on Monday morning and some people may even suffer until Wednesday, a report in the journal Applied Ergonomics revealed. A study at Rush University in Chicago found that even a two-hour change to your sleep pattern at the weekend affects reaction time and memory. If this is constant it can cause you to pile on the pounds, smoke and rely on caffeine to get you through the day. Lead researcher Helen Burgess said: "The weekend sleep in is just the process by which people shift their clocks later - it wouldn’t be a problem except for that rude awakening on Monday morning when all of a sudden we need to shift earlier." Some may not be able to change their sleeping habits but at least they now have a real excuse for their bleary eyes on Monday mornings.