Friday the 13th is a day that strikes fear into the hearts of many. While few are likely to worry about coming face-to-hockey-masked-face with Jason Voorhees and his gleaming machete, a number of people will alter their daily activities on that day, refusing to go to work, fly on an airplane or, in some extreme cases, even leave the house, in an attempt to avoid becoming victims of bad luck. And not a small number, either, as it has been estimated that $800-900 million is lost in business each Friday the 13th as a result of superstition-fueled consumer avoidance.

Dubbed paraskavedekatriaphobia – try using that one in Scrabble sometime – the fear of Friday the 13th affects an estimated 17-21 million people in the United States, according to the Stress Management Center and Phobia Institute in Asheville, North Carolina. It is an extension of triskaidekaphobia, the fear of the number 13. Symptoms can range from mild anxiety to full-scale panic attacks.

There are a variety of theories concerning the origins of Friday the 13th’s infamy. Biblical scholars trace the bad reputation of the number 13 back to Judas Iscariot, Jesus’s betrayer, who was the thirteenth guest at the Last Supper. As for the negative connotations of Friday, it is held to be the day that Jesus was crucified.

Another origin theory for the number 13’s ominous nature relates to a Norse myth about twelve gods having a gathering at Valhalla, which was crashed by a thirteenth guest, Loki, the god of mischief. Once there, Loki arranged for the murder of Balder, the god of joy, plunging the Earth into a period of darkness.

Yet another is derived from the numerological belief that 12 is a “complete” number, given that there are 12 months in a year, 12 signs of the zodiac and 12 apostles of Christ. Because 13 exceeds 12 by one, it is thought to be the number that offsets the balance of things, creating disharmony.

The fear created by the number 13 is prevalent in today’s society. Many hotels purposefully omit their thirteenth floors. Some airports lack a thirteenth gate, and hospitals often fail to include rooms numbered 13. These omissions are made to calm the fears of those made uneasy by the number.

I myself possess a fear of the number 13. While it is not an all-consuming fear, nor even especially disruptive to my day-to-day lifestyle, I do consciously attempt to avoid coming into contact with the number whenever I possibly can. At the gym, while using the treadmills and elliptical machines, I make an effort to look away from the monitor before the number appears in the time, calorie or distance counters. I feel a quick, but noticeable nervous twitter in my stomach each time I see the number on a digital clock (twice as much if it reads 1:13 p.m. as that is 13:13 in military time). I silently freak out when I check my email and see that 13 messages await me in either my inbox or Spam folder. It requires a truly amazing song to get me to listen to the thirteenth track of any given CD.

While I do, in fact, leave the house and function normally on each Friday the 13th, there is a muted sense of discomfort in the back of my head that remains until the official onset of Saturday the 14th. I could not say with any certainty why the anxiety exists within me. Perhaps the root of it has something to do with my birthday being the 13th of November. Or maybe it began on the Friday the 13th that occurred when I was in fourth grade, where I was late to school and lost my “Ghostbusters” lunchbox. It’s difficult to say.

Dr. Lee Berrigan, a Sacramento State psychology professor, said that, while he is not an expert in phobias relating specifically to Friday the 13th, he was willing to speculate that perhaps people who were afraid of the day might also be afraid of bad things happening to them in other circumstances. He believes that is a hypothesis that would warrant further investigation.

“You would want to investigate the general expectancies of bad things happening to these people. I would expect that people who would expect bad things to happen to them would generally be more likely to be afraid of Friday the 13th,” Berrigan said. “I am unaware of any empirical evidence that more bad things happen to people on Friday the 13th.”

One way of looking at the matter is to realize that bad things happen to people every day. If one consciously seeks out instances of “bad luck” occurring on Friday the 13th, he or she will certainly find them, making it, as Berrigan calls it, “a self-fulfilling prophecy.” Berrigan suggests that those grappling with the fear learn to let go of it and end their incessant worrying.

“People who have a positive outlook are generally happy and enjoy life more,” Berrigan said.

However, for those paraskavedekatriaphobics out there who simply cannot convince themselves that Friday the 13th is not some dark, oppressive force seeking to destroy them, folklore offers a handful of remedies to ward off bad luck on the date. One such countermeasure is to climb to the top of a mountain and burn every pair of socks you own that has holes in them. Good luck with that.

Brandon Wolfe can be reached at [email protected]