Everyone is scared of something, and sometimes those fears make an appearance in dreams.

Whether they include creepy images like snakes and spiders, or cause the anxiety of missing a deadline, those dreams can torment people during sleep. However, one may stop and wonder if they mean something.

Picture this:

You are running as fast as you can, but your legs are not moving.

The screams you hear, the horrors you say may seem as if it is all really happening.

Then you wake up relieved to realize it was all just a bad dream.

“Physiologically, it looks just like we're awake. Our brain activity looks just like wakefulness,” says Neurologist Charles Wells, who specializes in sleep studies.

Dr. Wells points out that people do not as often remember the good dreams.

“It seems striking to me that a significant portion of our dreams are somewhat unpleasant,” he says.

Wells explains people dream during a period called REM Sleep, which stands for “Rapid Eye Movements.”

Unlike other voluntary muscles, the eyes move and participate in the dream, just as they would when the person is awake.

People remember their dreams when they wake up during this sleep phase.

Dr. Wells says doctors know what is going on physically during REM sleep. However, medical professionals still do not know why people dream.

A common idea, he says, is brain categorizing and sorting, but nothing has ever been proven.

“It's a very difficult thing to study in a scientific way. All of it is somewhat controversial,” he says.

The images that manifest during sleep may not be real, but Psychologist Daphne Stevens says they could have real meaning.

“The important dreams are the ones that are haunting, that do either disturb us or, sometimes, reassure us,” Stevens says.

She believes dreams can function as a way for subconscious thoughts to grab someone’s attention.

Sometimes it is a literal translation, but more often, Stevens says, it is more symbolic.

“What is it that this symbol reminds you of in your personal life? What experience have you had?”

No two dreams look the same, but Stevens sees common themes in nightmares and offers her thoughts on what they mean.

One common nightmare, she says, is being chased by someone or something

“Some type of wisdom is trying to get to you,” Stevens explains. “You experience it in the dream with fear, because, deep down we’re afraid of change. We’re afraid of growth.”

Another nightmare is drowning or being flooded.

“There's something bubbling up from the unconscious that's really needing our attention. We are being flooded out with too much information,” she says.

Stevens says nightmares involving death are also common.

“Dreams about death are very often dreams about transition. The world as I know it is falling apart and this whole other thing is coming into being.”

Many times stress, anxiety, or other emotions trigger the nightmares

“I think some of the richest work that we can do is just to explore and be curious about our dreams,” says Stevens.

In other words, it might take looking at daily fears to suppress the images that haunt us at night.

The next time you wake up with your heart pounding or sweat dripping, remember the dark has a way of bringing our fears to light.

For those that struggle with bad dreams or simply want to see what they might mean, Stevens encourages keeping a journal detailing what their dreams involved and looking for common themes.