The third Monday in January (yesterday) is widely referred to as Blue Monday; so-called because it’s when Seasonal Affective Disorder (SAD) and general winter blues are thought to be at their peak. But despite catching the popular imagination, is there any scientific or medical proof to support Blue Monday being the most depressing day of the year? In a nutshell, no, there isn’t. Blue Monday was actually invented by psychologist Cliff Arnall in 2005. It is said that Arnall came up with the idea of Blue Monday as part of a marketing campaign for British travel company Sky Travel (now defunct). Arnall used a mathematical equation that took into account a variety of factors to determine which was the saddest day of the year. One factor included was Northern Hemisphere weather data and Sky Travel used Arnall’s findings to persuade people that the only way to beat the winter blues on Blue Monday was by heading south of the equator. So, Blue Monday is nothing more than an elaborate marketing tool really, designed to encourage people to go on holiday. But that hasn’t stopped it becoming a phenomenon that’s talked about every year mid-January. In an interview with The Telegraph back in 2010, Arnall said people should ignore the most depressing day of the year label and try to be cheerful. “I was originally asked to come up with what I thought was the best day to book a summer holiday, but when I started thinking about the motives for booking a holiday, reflecting on what thousands had told me during stress management or happiness workshops, there were these factors that pointed to the third Monday in January as being particularly depressing," said Arnall. How did you feel yesterday? Any bluer than usual?