Perhaps you woke up on Monday morning feeling lower than low.

No, I’m not talking about the typical beginning-of-the-work-week form of lowness, but more of a deep-down-in-the-bones kind of blues that made you want to pull the blankets over your head and hide out for the day. If so, there’s a British psychologist who not only could feel your pain from across the ocean, he believes he has determined the very source of it.

According to Dr. Cliff Arnall, who specializes in seasonal affective disorders at the University of Cardiff, in Wales, the reason for your malaise is that Jan. 23 just happened to be the most depressing day of the year, the bluest of Blue Mondays. That’s right, and Arnall, quoted often in the British press as an expert on everything from self-confidence to sleep disorders, has even devised a handy formula that purports to explain how he’s able to peg the gloomiest day on the calendar. For the math-minded, it looks like this:

[W + (D – d)] x TQ

———

M x NA

The equation is broken down into seven variables: (W) weather, (D) debt, (d) monthly salary, (T) time since Christmas, (Q) time since you failed to quit your bad habits, (M) low motivational levels, and (NA) the need to take action.

In other words, Arnall explained, while the days technically get longer after Dec. 21, cyclonic weather patterns emerge in January, bringing nasty stretches of dark and depressing cloudiness. The majority of people already broke their healthful New Year’s resolutions – losing weight, quitting smoking, exercising regularly – which typically happens six to seven days after they’ve made them. If that weren’t depressing enough, he said, now that the happy holidays are past, and with them those wonderful three-day weekends, people have little to look forward to but going to work and worrying about bills.

“Following the thrill of New Year’s celebrations and changing over a new leaf,” he remarked to MSNBC.com, “reality starts to sink in. The realization coincides with the dark clouds rolling in and the obligation to pay off Christmas credit card bills.”

Arnall has gotten a lot of publicity around the world – much of it bad, of course – since he came up with his nifty formula last year, when the worst day fell on Jan. 24. Health experts have come forward to suggest that anyone who attempts to pinpoint the single gloomiest day of the year is dabbling in quackery. Why pick on Jan. 23, the experts ask appropriately, when the entire month can be a major downer for a third of the population of Britain, and the more than 100 million Americans who live with seasonal affective disorder?

The noted Cardiff psychologist, however, appears to have little time for such professional nitpicking. He’s much too busy creating scientific equations that can tell us exactly why we feel the way we do on certain days. Not content to calculate the most depressing day, Arnall also has determined that June 24 will be the happiest day. Using the variables Outdoors, Nature, Social Interaction, Childhood Summers/Positive Memories, Temperature, and Holidays, here’s his equation for happiness:

O + (N x S) + Cpm

———

T + He

Just do the math. I’m too bummed out to explain.