What’s the Difference Between Nightmares and Sleep Terrors?
Everyone has bad dreams. It’s like a scary movie playing in your mind, typically waking you up right before something terrible happens—like falling off a cliff or witnessing a murder—relieved when you realize it wasn’t real. But did you know there are actually two types of sleep conditionsthat fall under the “bad dream” umbrella? Nightmares and sleep terrors (also called night terrors). We’ll dive into both, and cover some ways you can stop having them.
Nightmares are unpleasant dreams that you usually remember upon waking, while sleep terrors involve feelings of intense fear, screaming, and thrashing around while you’re still asleep.
There are few things that set nightmares and sleep terrors apart. For starters, you typically remember your nightmares—maybe not every detail, but you can remember that you’ve at least had one. But with night terrors, you could wake up and have no idea it occurred. The episode is typically remembered by your bed partner (hard for them to sleep through the screaming!), but not by you. So, if you sleep alone, you could have sleep terrors and not even know it.
A nightmare tends to get scarier gradually, not right away. Think of it like a scary movie—there tends to be a build up. Sleep terrors are different. You can be sleeping calmly, and all of a suddenyou’re afraid and screaming.
This is partly due to the stage of sleep the event happens in. Nightmares occur during rapid eye movement (REM) sleep. This is the stage of sleep when vivid dreaming is most likely to happen, according to the American Sleep Association (ASA), and the brain is more active than it is during other stages of sleep.
Sleep terrors typically happen during non-REM sleep, specifically stage three sleep. This stage is also called deep sleep, where according to the ASA, extremely slow brain waves start to appear, interspersed with faster waves.
Because nightmares and sleep terrors happen during different stages of sleep, they also happen at different times of night as a result. Stages three and four sleep usually happen during the first half of the night, and REM sleep during the second half. So when I’m caring for a patient, I always ask about the timing of the event. If it happened during the first half, I’ll consider sleep terrors, and if it happened in the second half then I’ll lean towards nightmares.
I’ll also want to know if my patient was easy to reassure after the event. It’s easier to comfort someone who just woke up from a nightmare than a sleep terror. They’re awake, coherent, and can be reassured. They’ll realize they had a nightmare and it was just a dream. Sleep terrors are different. They can’t be comforted, and they may not even notice someone else is in the room with them. This happens because they’re only partially awake—much of their brain is still asleep.
So why does your brain play such terrifying tricks on you when you’re sleeping?
According to the National Sleep Foundation, there are a few things that increase the likelihood of having a nightmare, including eating before bed (your metabolism kicks in, keeping your brain active), medications including certain antidepressants, lack of sleep, sleep disorders like restless leg syndrome, and stress. Recurring nightmares, or bad dreams where the same theme or events play out, are especially prevalent among trauma survivors and people with PTSD, according to the U.S. Department of Veterans Affairs.
Not as many people have experienced sleep terrors, but about 10 percent will have one in their lifetime. Sleep terrors tend to affect kids more than adults, according to The Mayo Clinic. Almost 40 percent of children will experience sleep terrors, but most outgrow them by their teen years.
According to the Mayo Clinic, a few things can trigger sleep terrors including sleep deprivation, stress, fevers, and changes in sleep schedule (like travel or jet lag). Sleep apnea, restless leg syndrome, and alcohol use can also increase the likelihood of sleep terrors.
Sleep terrors are more common in people with mood or anxiety disorders, including PTSD. They’re also more prevalent in people who sleep walk and/or talk. This is because sleep terrors, sleep walking, and sleep talking are thought to have similar underlying mechanisms in the brain during sleep; they also tend to occur during the same stages of sleep.
There are a few ways you can try to prevent nightmares and night terrors.
For mild cases of nightmares, I recommend something called image rehearsal therapy. It works by desensitizing the nightmare so it’s less scary. During the day, write out your nightmare, remembering the early details. But near the end of the story, during the most frightening part, create a non-scary ending. Now you have a story that starts out like your nightmare, but has a safe ending. Visualize this story a few times a day. When the story appears in your nightmare, the ending should change to be more like the one you’ve created. This may extinguish the nightmare over time.
Sleep terrors are treated differently. I recommend mapping the timing of sleep terrors and setting an alarm before they strike. Part of this rests on your bed partner, because they’re the ones that know when your sleep terrors happen. Ask them to keep track of the time of events so you know when to set the alarm. Wake up with the alarm and go back to sleep. In some cases, I’ll have a patient do an overnight study in a sleep lab, where your behavior will be videotaped and your brain waves, breathing, and heart rate will be monitored.
In more serious cases, sleep terrors can include getting out of bed (sleep walking), which can lead to physically harming yourself. If you’re having a combination of sleep walking and sleep terrors, it’s most definitely time to see your doctor. They will give you additional advice to make the bedroom safe, like sleeping on the floor, using a sleeping bag, or setting alarms on doors and exits.
Remember that someone having a sleep terror may not be reassured by another’s presence. So don’t confront someone having a sleep terror, as they could get violent. Once a sleep terror starts, there isn’t much you can do to stop it. Instead, clearing the environment of dangerous objects is the best you can do until it’s over.
If you’re experiencing frequent, troublesome nightmares, or you’re just not feeling like you’re getting restful sleep, it may be time to see a sleep doctor.
Even though nightmares are common, it’s time to see a doctor when they start to affect you during the day. Are you feeling sleepy during the day because the nightmares are keeping you up, or because you’re avoiding sleep due to bad dreams? Are you having a hard time focusing at work? Then, yes, it’s time to see your doctor.
Using how you feel during the day as a signal to see your doctor works for sleep terrors too, especially because you won’t always know that you’ve had one. If you’re sleepy during the day, unfocused, or have trouble functioning normally, it’s time to talk to your doc. You might also notice unexplained injuries or bruises from thrashing around during a sleep terror—another sign that you should see your doctor.
Serious cases of nightmare disorder, a type of parasomnia, require specialized help like cognitive behavioral therapy. Your doctor will work with you to tackle the source of the nightmares, including trauma, stress or anxiety, alcohol or drugs, or other underlying sleep disorders, according to the Mayo Clinic.
Sleep is one of the body’s most important processes, and nightmares and sleep terrors can majorly mess it up. So if you’re experiencing either and they aren’t going away on their own, talk to your doctor. You won’t be stuck in a cycle of bad dreams forever.
Nitun Verma, M.D. is a sleep medicine physician trained at Stanford University. He’s a spokesperson for the American Academy of Sleep Medicine and practices at Crossover Health in the San Francisco Bay Area.