What Is the Difference Between Paradoxical Sleep and Paradoxical Insomnia?

Paradoxical sleep and paradoxical insomnia might sound like the same thing. But in fact, they describe two totally different concepts.

The confusion might be all thanks to that word, paradox, which means a self-contradictory statement. For example, a phrase like "The silence is deafening" is a paradox because the statement shouldn't make sense on its own. How can silence ever be loud? Well, if you've ever made a joke that didn't quite land, the lack of ensuing laughter probably said a lot about your undervalued comedy skills. Ironically, the silence made the truth more apparent than words ever could.

So, what makes sleep and insomnia paradoxical? We start by discussing how REM sleep became known as paradoxical sleep and why it's so important. Then, we'll talk about the conundrum of paradoxical insomnia—and what to do if you know you're not sleeping well.

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What is Paradoxical Sleep?

Paradoxical sleep refers to rapid eye movement (REM) sleep, the fourth, final and deepest stage of sleep. Overall, REM sleep makes up a quarter of our time spent sleeping. The first iteration starts about 90 minutes after we have fallen asleep and lasts for about 5 minutes. We then cycle through the other stages, with each iteration of REM sleep becoming progressively longer.

REM sleep is so important, it is regarded "as a third state of existence, distinct from both sleep and wakefulness," writes medical journalist Lynne Lamberg. In fact, its discovery in 1953 is what led to the establishment of sleep medicine as a separate field altogether.

If the idea of REM sleep seems mundane to us in the 21st century, then let's put it in historical perspective. In the early 1900s, scientists assumed the brain went passive when humans and animals slept. Like an engine idling in a parked car, the brain was "turned on," but it did nothing.

People had also known that the eyes moved rapidly underneath the eyelids sometime during sleep. Anyone who has watched a baby sleep for long enough could see it happening. Apparently, Edgar Allan Poe had referenced REM sleep in "The Raven," when he said the bird's eyes "have all the seeming of a demon's that is dreaming." So for a long time, REM sleep had no significance outside the erratic witnessing of dreams.

Yet as recording devices became more precise, scientists discovered surprisingly large amounts of electrical activity in the brain during REM sleep. And not just in any part of the brain, either—in the cortical and subcortical areas, the topmost parts of the brain associated with conscious thought, movement, memory, and other higher-order functions.

These findings are what led French neuroscientist Michel Jouvet to coin the term paradoxical sleep in 1959, after his own study on the sleeping behavior of cats. In fact, Jouvet was the first person to map the areas of the brain involved in REM sleep. In particular, he found that neurons in the pons—the "bridge," in Latin, of the brainstem—not only triggers paralysis in the body's muscles during REM sleep, but it also activates the parts of the brain that are thought to be linked to dreaming.

To Jouvet, the paradox of REM sleep laid in this increased brain activity. Had you not known that the person was sleeping, the activity would have made you think the person was awake.

While paradoxical sleep forever changed our understanding of sleep, mysteries still surround its role in early human development and across the lifespan. Scientists think it is essential for five main reasons:

• Eyesight. When we sleep, neural activity in the thalamus—the part of the brain that receives and transmits all sensory signals (except for smell)—pulses and pauses in sync with activity in the visual cortex. This is much different from when we're awake, when both the thalamus and visual cortex show continuous activity. Combined with the rapid movement of the eyes, this electric pulsation might be what strengthens the connection among the neurons involved in eyesight, thus helping us see better.

• Bodily Movements. Despite the rest of the body seeming catatonic, the eyes and limbs still twitch during paradoxical sleep. This overall paralysis was once thought to prevent people and animals from acting out their dreams. But once scientists learned that dreams are not exclusive to paradoxical sleep, they stopped supporting that idea. Instead, they now believe that paradoxical sleep is involved in sensorimotor development. In other words, it strengthens babies' connection between their bodies and brains, giving them a better grasp of what their limbs can do.

• Learning and Memory. In addition to helping us navigate physical spaces, the hippocampus—another part of the brain—also converts short-term memories into long-term memories. Like with the visual cortex, the hippocampus shows a lot of brain wave activity during paradoxical sleep. While it's not yet clear whether paradoxical sleep specifically helps us remember fact-based information (like the capital of a country), it does help us learn tasks that feel automatic over time (like driving a car). So with proper sleep, our overall memory is improved, thus giving us better judgment.

• Emotional Regulation. While activity in the visual cortex and hippocampus go up during paradoxical sleep, activity in the amygdala—the part of the brain associated with fear, stress and anxiety—goes down. At the same time, its connection to the hippocampus becomes activated. This could mean that paradoxical sleep helps us strip the emotional baggage from our memories before they become consolidated. In other words, it helps us start fresh the next day.

• Energy Allocation. Endotherms—an animal group that includes humans, other mammals and birds—are able to regulate their own body temperature. This is in contrast to reptiles, amphibians and most other animals, who get their warmth from the sun. But when humans enter paradoxical sleep, we temporarily lose the ability to thermoregulate. Because generating heat takes most of our energy, some scientists believe that paradoxical sleep helps us reallocate this energy to the growth, maintenance and repair of cells.

So if paradoxical sleep is what we want, then paradoxical insomnia is what we should avoid. Problem is, we don't quite know how.

What is Paradoxical Insomnia?

Paradoxical insomnia is a condition that has generated a lot of controversy. Most people who test for insomnia disorder show some kind of physiological sleep disturbance, whether it's in their heart rate, breathing, or muscle movements. But when hooked up to the same device, people with paradoxical insomnia appear to sleep just fine. And throughout the next day, they seem to act and think as if they have gotten enough sleep. Yet they still complain about not sleeping well.

The lack of objective evidence for paradoxical insomnia is exactly why it's controversial. Previously known as subjective insomnia or sleep state misperception in the 1990s, the name changed in 2005 with the publication of the International Classification of Sleep Disorders second edition (ICSD-2). This term is more accurate than the previous names. After all, most people with insomnia disorder tend to underestimate the time they spend sleeping and overestimate how long it takes them to fall asleep. So, misperception is not exclusive to paradoxical insomnia.

Clinicians had a difficult time diagnosing patients with paradoxical insomnia based on this insufficient criteria. So in 2014, the manual's third and latest edition (ICSD-3) categorized paradoxical insomnia and 10 similar conditions as subtypes of insomnia disorder. While this decision made the seriousness of insomnia disorder more apparent, it relegated paradoxical insomnia to a lesser status.

How do people get paradoxical insomnia? No one knows yet. Clinical psychologist Dr. John Cline suspects it might have to do with people's attitudes towards sleep. Anticipating yet another night of inadequate sleep might heighten the brain's awareness during rest. As a consequence, this makes sleep feel more shallow, even though the person managed to achieve deep sleep.

But is it just high expectations? More recently, psychiatrists in the United States and Iran reviewed 40 studies on paradoxical insomnia. In addition to personality traits, these studies suggest irregular brainwave patterns, altered metabolizing of glucose—the brain's main energy source—and psychiatric symptoms as possible underlying causes. To be sure, further research needs to be done with tools that can detect these indicators more adequately.

What Can I Do if I'm Worried About My Sleep?

So we want paradoxical sleep, but we don't want paradoxical insomnia. When all signs point to the contrary, the feeling that you haven't slept well can be isolating. If you do feel like your sleep has been too shallow lately, here are some things you can do.

Proper sleep hygiene is a good first step. Some habits include waking up and going to bed at the same time each day, limiting your caffeine intake, and relaxing an hour before bedtime. Sleep hygiene can help treat and prevent mild insomnia, but for more chronic cases, it might not be enough.

Retraining how your mind approaches sleep might be another option. If you feel like you are not getting enough deep sleep, it might be because of negative attitudes towards sleep that keep you alert during the night. Cognitive behavioral therapy (CBT) can help people realign their thoughts and actions towards more productive sleep goals. In fact, CBT has proven to be more effective at treating insomnia than just medication alone.

Sleep restriction therapy is one type of CBT that has produced great results for people with insomnia. This method involves restricting the time spent in bed so that the patient can re-associate the bed with rest. If this sounds counterintuitive, then read our article at the link to learn more.

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