A mathematical formula devised by an academic claims that today - the third Monday of January - is when the nation's collective well being will sink to an all-year low.
'Blue Monday', as it has been dubbed, is said to be the most depressing day of the year.
Mental Health Research UK (MHRUK) says 'Blue Monday' occurs due to a combination of bad weather, debt, the need for a Christmas detox and poor motivation.
The term was coined after UK psychologist Cliff Arnall created a mathematical formula to identify elements contributing to a general feeling of 'mid-winter blues' in 2005.
But whether there is any truth to the theory is a source of contention, since Arnall created the formula as part of a marketing campaign for a travel company.
The hashtag #bluemonday has been trending on Twitter with users taking to the site to discuss the theory and suggesting ways to combat it:
Marketing Week reports that some businesses are also running promotions, competitions and deals to coincide with 'Blue Monday'. Halifax is running a promoted tweet on Twitter and Coconut water brand Vita Coco is giving away 'experiences' to combat the 'January blues'