There are so many common myths, misconceptions, and urban legends that it can be fun to learn about them and pass that knowledge on to others. Because they’re so ingrained in society—drilled into our heads from the time we’re children—we don’t know they’re untrue until we learn they are.

One common myth is that suicide rates increase around Christmastime. Some versions of this myth may say the rate doubles, others will cite a percentage. The truth is that suicide rates actually go down over the holidays. In fact, more suicides take place in the early spring than at any other time of the year. No one really knows why, but it probably has to do with people being around others during the holidays. People often get depressed in the winter time before the holidays (the weather, lack of sunlight, social hibernation, stress of the holidays, money problems, etc).

But then the holidays arrive and suddenly they’re propelled into a world of food and music, gift-giving, parties, and gatherings. They’re surrounded by people and merriment. Maybe they feel better for a while and their suicidal thoughts go on hiatus. When the holidays pass, life returns to normal, and the depression returns. Maybe these people think if they can just fend off their harmful thoughts until the spring, they’ll be okay; they just need to make it through the winter. But when spring arrives they’re still depressed and suicidal and that’s when they decide to finally end it all. It’s one theory.

One of the myths that people often espouse, especially in the winter time, is that we lose 80% of our body heat through our heads. (Or 50%; the number changes.) The truth is, we do lose most of our body heat through our extremities—arms and hands, legs and feet, and heads. But we don’t lose any more body heat through our heads than we do our hands. It’s just that many people don’t wear hats in the winter, so when they do wear them they feel warmer. If you never wore gloves and suddenly put on gloves, you’d feel warmer too. Or shoes. Or pants.

People often see veracity in this myth because “heat rises.” While it’s true that hot air rises above cool air, heat does not rise inside our bodies and out through our heads.

Here’s a good one: If you shave, your hair will grow back faster, thicker, and darker. This was once debunked on a Canadian kids show called Street Cents years ago. Shaving just cuts hair—it has no effect on the part of the hair shaft below the skin surface, which is where growth and pigmentation occur. No one believes that when they get the hair on their head cut that it will grow back thicker and darker, so why do they believe it’s true with the hair on their legs? The truth is, hair does not grow back thicker or darker, it just may appear so because the new hair growth has blunt ends (from being cut) instead of tapered ends.

Speaking of hair, how about the common notion that hair and fingernails continue to grow after death? This one’s false too. Just like the above, hair and fingernails may appear longer after death simply because the skin around them has retracted. Dehydration causes the skin and soft tissue to shrink, but the hair and nails remain the same length. It’s an illusion.

A myth that knuckle-crackers will love to bust is that cracking your knuckles causes arthritis. I read the truth about this myth when I was a kid, in a magazine at my doctor’s office and current research corroborates it: Your joints are surrounded by a thick lubricating fluid. When you crack your knuckles the bones of the joint pull apart, which causes a gas bubble to form in between. The sound you hear that so many people find irritating is the sound of the adhesive seal in the joint breaking (or you can think of it as the bubble popping). For the record, arthritis is caused by a person’s immune system attacking their joints.

Fun, right? Now go forth and start propagating the truth about these common myths.

This article originally appeared in a slightly altered form as a blog post.