If you're wary of Friday the 13th, you might have friggatriskaidekaphobia.
The Stress Management Center and Phobia Institute in North Carolina estimated that 17-21 million people were affected by friggatriskaidekaphobia in the early 2000s.
National Geographic reported that in the early 2000s, an estimated 17 - 21 million people had friggatriskaidekaphobia, according to the founder of the Stress Management Center and Phobia Institute in North Carolina, Donald Dossey.
Symptoms of friggatriskaidekaphobia are high anxiety, panic attacks, nausea, dry mouth, and loss of control.
But where does the fear come from?
There are different theories out there, one dating back to the late 19th century. According to TimeandDate.com, the day was mentioned in a biography of Italian composer Gioachino Rossini, who passed away on a Friday the 13th. Also, a book from 1907, written by businessman Thomas Lawson, was titled Friday the Thirteenth.
Other theories focus on the number 13 going beyond the completeness of what we're used to, because the number 12 is so significant, according to AllAboutCounceling.com. For instance, there are 12 hours in a day, 12 months in a year, 12 apostles, 12 zodiac signs, 12 days of Christmas, etc.
National Geographic noted even another theory relating to a Norse myth about 12 gods whose dinner party was destroyed by an uninvited 13th guest.
As for Friday, it's known as the day Jesus was crucified. Also, some scholars believe it was the day involved in original sin of eating the forbidden fruit.
For those who suffer from friggatriskaidekaphobia, Dossey recommends focusing on pleasant thoughts.
Psychologist at the University of Hertfordshire, Richard Wiseman, said curing friggatriskaidekaphobia "need to realize that they have the ability to create much of their own good and bad luck," according to National Geographic's report. "And they should concentrate on being lucky by, for example, looking on the bright side of events in their lives, remembering the good things that have happened, and, most of all, be[ing] prepared to take control of their future."