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Why do we have intense dreams when we're sick?

Why are dreams more intense when you're sick?
Why are dreams more intense when you're sick? 02:53

MINNEAPOLIS — Our busy lives can make a good night's sleep hard to come by. Feeling under the weather can make it worse and sometimes downright scary.

"I definitely have memories of being sick and having very vivid scary dreams," one woman told WCCO. "For me it's always being in a building, where I don't know where the exit is, and it feels like somebody is chasing me."

"It usually involves clowns, many clowns," said one man as he described his fever dreams. "These clowns are not the good kind."

No matter the intense dream's story line, their appearance feels tied to whether you're sick.

Dr. Mark Rosenblum is a sleep psychologist with Hennepin Healthcare — helping people get over disorders that interrupt their ability to catch some sleep.

Why do we have intense dreams when we're sick? There could be a couple of variables involved. 

"One has to do with something called REM sleep," said Rosenblum.

REM stands for "rapid eye movement." It's the stage of sleep when dreams happen. "If someone's not getting enough sleep, they get what's called REM rebound on the following nights. And when we have REM rebound, what we'll find is all our dreams tend to be very intense," he said.

During REM, people can't regulate their body temperature. And if you have a fever, the heat can impact how your brain processes thoughts. 

"So, when you put these things together, the outcome is people have these really just crazy, wild dreams," said Rosenblum.

Why can fever dreams often be stressful or negative? The answer isn't exactly known, said Rosenblum, but they there are some potential causes. 

"If I'm really stressful, and even if I do fall asleep fine, oftentimes I'll find I have more stressful dreams," he said. Feeling under the weather makes a person stressed, thus leading to stressful dreams. 

"We're uncomfortable, we're unhappy, so there's a carryover there," he said.

How can we prevent or limit these types of dreams when we're sick? Rosenblum had three suggestions. First, prioritize getting a good night's rest. A lack of sleep raises the chance for intense dreams.

Secondly, try to relax before bed. Less stress equals less likelihood of a stressful dream. Whatever helps you wind down or ease your mind, whether it's a book or TV show, find a way to relax.

Lastly, keep cool when sleeping. Lowering your body temperature, especially around your brain, can calm those dreams.

"Don't turn off the air conditioning until you're up for good in the morning," said Rosenblum.

Nightmares are somewhat different from fever dreams. While they both happen during REM, nightmares are typically connected to a history of trauma in one's life.

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