It sounds like the beginning of a corny joke: Sleep, a circadian rhythm, and a mood disorder enter a brain …
But this is actually quite serious: Their relationship to one another is complicated. If one is out of balance with the others, your mental health may suffer.
Consider this 2019 study in mice, which revealed that sleep is a sensitive and early marker of the brain’s ability to respond to challenges faced during wakefulness. Rapid eye movement (REM) sleep—the state in which we dream—may help to regulate our emotions and consolidate our memories, and possibly plays an important role in the brain’s response to stress.
“REM sleep may be helping us prepare our brains to deal with the outside world,” says Ruth Benca, MD, PhD, Chair of Psychiatry and Human Behavior at the University of California Irvine, and a member of Genomind’s Scientific Advisory Board. “There’s also probably the fact that certain kinds of instinctual behaviors may get rehearsed in REM sleep.” For instance, how we deal with stress.
Sleep, Mental Health, and Their Complicated Relationship
First of all, you should know that REM sleep is a more activated brain stage. “Sleep seems to be important for brain plasticity—some of the functions probably include putting memories into longer term storage and solidifying memories,” Dr. Benca says. Certain kinds of instinctual behaviors may get rehearsed during this sleep stage. Early in development, REM sleep is a much larger chunk of our sleeping time, and it may be essential for the brain to wire itself properly, and therefore, aid in its development.
So while researchers are just starting to understand sleep functions, it appears that REM sleep is a critical component. And here is where the relationship between sleep and mental wellbeing isn’t well-defined.
For instance, in various types of dementia, particularly in Alzheimer’s disease, there is a loss of REM sleep. Whether it is the lack of REM sleep that contributes to the disease and its symptoms, or whether the disease causes the deficiency in REM sleep, is not known. The question of which comes first is also a question when looking at the relationship between sleep and mental health conditions.
On the other hand, NREM (non-REM) sleep, which makes up the majority of sleep time in adults (75-80%) includes two important sleep EEG oscillations: slow waves and sleep spindles. Both have been implicated in learning and memory, and one of the important functions of NREM sleep, and slow waves in particular, is to help reset or normalize brain synapses. During wakefulness, brain synaptic strength increases, and during sleep, some synapses are eliminated, which allows for brain plasticity through renormalization of overall synaptic strength.
Sleep and Psychiatric Disorders
“There’s a lot of epidemiologic evidence that insomnia, in particular, often precedes new onset or exacerbation of psychiatric disorders, particularly mood disorders,” Dr. Benca says. People who have chronic insomnia are more likely to develop depression than people who don’t have any sleep problems, and excessively sleepy individuals may also be at greater risk for developing a psychiatric illness.
“Sleep problems are often but not always a leading edge of psychiatric disorders. And on the other hand, when people are acutely psychiatrically ill, that can contribute to their sleep problems,” she says.
How Better Sleep Can Improve Symptoms
When talking about sleep and mental health issues, the quantity, quality, and timing are important. Sleep is governed by timing, or circadian rhythms, which helps determine retire and wake behavior.
“We want to think not just about insomnia or sleep amount, but understand that there is a timing component as well,” Dr. Benca says. Dysregulation of sleep and rhythms are common in mental health conditions. For example, people with mood disorders tend to have a more delayed sleep phase—they are night owls, sometimes in the extreme, so it isn’t just that they have insomnia and cannot sleep, but that they can’t sleep during the right time of the day. Furthermore, many psychiatric disorders have been associated with alterations in circadian clock genes.
For some mental health conditions, addressing these social rhythms through therapy could help diminish symptoms. There is data surrounding bipolar disease and depression that shows this is the case. Improving sleep—the quantity, quality, and timing—may help mental wellbeing.