Blue Monday is a name given to a day in January (typically the third Monday of the month) claimed to be the most depressing day of the year. The concept was first publicised as part of a 2005 press release from holiday company Sky Travel, which claimed to have calculated the date using an equation.

The idea is considered pseudoscience, with its formula derided by scientists as nonsensical.

It is worked out with a formula taking into account six factors: weather, debt, time since Christmas, time since failing our New Year’s resolutions, low motivational levels and the feeling of a need to take action.

One equation used by Arnall in 2006 was:[2]

Where Tt = travel time; D = delays; C = time spent on cultural activities; R = time spent relaxing; ZZ = time spent sleeping; St = time spent in a state of stress; P = time spent packing; Pr = time spent in preparation. Units of measurement are not defined.

The 2005 press release[7] and a 2009 press release[8] used a different formula:

where W=weather, D=debt, d=monthly salary, T=time since Christmas, Q=time since failing our new year’s resolutions, M=low motivational levels, and Na=the feeling of a need to take action. Again, no units were defined.

Ben Goldacre has observed that the equations “fail even to make mathematical sense on their own terms”, pointing out that under Arnall’s original equation, packing for ten hours and preparing for 40 will always guarantee a good holiday, and that “you can have an infinitely good weekend by staying at home and cutting your travel time to zero”.[2] Dean Burnett, a neuroscientist who has worked in the psychology department of Cardiff University, has described the work as “farcical”, with “nonsensical measurements”.[9]

Further online calculations have factored in location for hours of sunshine and socioeconomic activity which impacts cities such as Detroit (USA), Birmingham (UK) and Tromso (N) negatively

GPs say exercise and reading up on depression are ways to beat the blues.  “Yes, we do see lots of people with depression and anxiety in the winter months.  The message is it’s not a terrible disorder, people do get better,” Royal College of General Practitioners spokesman Dr. Alan Cohen said.

CBD has been long known to help manage mood disorders. Products such as Provacan that contain hemp-derived CBD are legally available across Europe without prescription or medical cannabis license.