Blue Monday (falling on January 15, 2018) is a term coined by Dr. Cliff Arnall in 2005 to describe the saddest day of the year. Possible contributions to this day could be holiday weight gain, debt from the holidays, failed resolutions and bad weather but Dr. Arnall actually created a formula for this particular day. While it is not totally scientific, it factors in the weather, level of debt, amount of time since Christmas, failing new year’s resolutions, low motivation, and the feeling of a need to take charge. Here is the formula:
[W + (D-d)] x T^Q} ÷ [M x N_a]
With ‘W’ standing for weather, ‘D’ standing for debt, ‘d’ standing for monthly salary,
‘M’ for motivational levels and ‘Na’ standing for the feeling of a need to take action.
While this day is dubbed the saddest day, it is important to note that there’s no actual research or scientific backing. There is, however, such a thing called seasonal affective disorder (SAD) which usually occurs in the winter months and is characterized by feelings of depression, low interest and energy, sleeping problems, changes in appetite or weight, and more.
Causes are unknown but are likely to include your circadian rhythm, serotonin and melatonin levels. Essentially, the lack of sunlight in the winter can mess with your serotonin levels (so people in the north experience SAD more frequently) but also it can disrupt your natural circadian rhythm which can in turn affect your melatonin levels.