Sleep is essential for the physical upkeep of the body, but it also helps maintain cognitive skills, such as attention, learning, memory, and emotional regulation.
Getting a good night’s rest even underpins our ability to perceive the world accurately. Research suggests that going completely without sleep for 3 or more nights in a row results in perceptual distortions, hallucinations, and delusions.
The latest discoveries about the importance of sleep for physical and mental well-being come at a time when technology is putting pressure on sleep time as never before. Social media, the internet, TV on demand, and video games are increasingly keeping us from our beds in the evenings.
The CDC advise that adults get between 7 and 9 hours of sleep a day, with the specific recommendation varying by age.
However, according to the 2012 National Health Interview Survey, almost one-third (29%) of adults in the United States sleep for less than 6 hours each night.
Poor sleep is a recognized risk factor for the development of a range of mental health issues.
A study that followed 979 young adults in Michigan, for example, found that insomnia was associated with a four-fold higher risk of depression 3 years later.
A review of research found evidence that insomnia preceded the development of not only depression but also bipolar disorder and anxiety disorders. The researchers also found a link between insomnia and an increased risk of suicide.
In 2020, a study published in JAMA Psychiatry identified an association between sleep problems in early childhood and the development of psychosis and borderline personality disorder in adolescence.
As well as increasing the risk of developing mental health problems, sleep disturbances are also a common feature of most mental illnesses, including anxiety, depression, bipolar disorder, and schizophrenia.
Prof. Daniel Freeman, a psychiatrist, and his colleagues at the University of Oxford in the United Kingdom believe that the two-way relationship between sleep problems and poor mental health can result in a downward spiral.
Writing in The Lancet Psychiatry, they say that doctors can be slow to address these issues in people with mental health problems:
“The traditional view is that disrupted sleep is a symptom, consequence, or nonspecific epiphenomenon of [mental ill health]; the clinical result is that the treatment of sleep problems is given a low priority. An alternative perspective is that disturbed sleep is a contributory causal factor in the occurrence of many mental health disorders. An escalating cycle then emerges between the distress of the mental health symptoms, effect on daytime functioning, and struggles in gaining restorative sleep.”
A form of cognitive behavioral therapy for treating insomnia (CBT-I) has proven its worth as a way to tackle this cycle of sleep problems and mental health conditions.
When Prof. Freeman and his colleagues randomly assigned 3,755 students with insomnia from 26 universities in the U.K. to receive either CBT-I or usual care, they found that the treatment was associated with significant improvements.
Students who received CBT-I not only slept better, but they also experienced less paranoia and had fewer hallucinations.
According to a 2015 meta-analysis, CBT-I may also be an effective treatment for anxiety and depression in people with insomnia.
The treatment involves educating people about sleep and aims to change their sleep-related behaviors and thought processes.
People learn about good sleep hygiene, which involves practices such as limiting daytime naps, avoiding alcohol, nicotine, and caffeine in the evening, and refraining from using digital devices at bedtime.
The behavioral techniques include:
- Sleep restriction: Reducing the time the person spends in bed to match more closely the amount of sleep they need.
- Stimulus control: For example, using the bedroom only for sex and sleeping, going to bed only when sleepy, and getting out of bed after 15–20 minutes of wakefulness.
- Relaxation: For example, tensing and relaxing the muscles while in bed, or focusing on the breath.
The cognitive techniques include:
- putting the day to rest, which involves setting aside time before bed to reflect on the day
- paradoxical intention, or trying to stay awake
- belief restructuring, which means addressing unrealistic expectations about sleep
- mindfulness, in which the person acknowledges their thoughts and feelings before letting them go
- imagery, which requires a person to generate positive mental images
Psychiatrists have proposed three interrelated factors to explain the close two-way relationship between sleep and mental illness:
- emotional dysregulation
- genetics, in particular relating to the circadian “clock” that regulates the sleep-wake cycle
- disruption of rapid eye movement (REM) sleep
Most of us have intuited from personal experience that a night of disturbed sleep can make us feel a little down and grumpy the next day.
Research backs up our intuition. A 2005 study of medical residents in Israel, for example, found that poor sleep increased negative emotional responses when the going got tough at work the following day. It also decreased positive emotional responses when things went well.
More recently, a study in Norway found that delaying going to bed for 2 hours, but still getting up at the normal time, stifled positive emotions, such as joy, enthusiasm, and a sense of fulfillment. This effect increased with every consecutive day of delayed sleep.
Relatively mild, temporary emotional disturbances of this sort can set in place a vicious cycle. Ruminating about the past day’s events, for example, or anxieties about tomorrow may prevent a person from falling asleep once again.
Individuals with a predisposition to a particular mental health condition and those who already have the condition may be particularly prone to this mutually reinforcing effect.
Someone with bipolar disorder, for example, might feel too “wired” to sleep during a manic episode. A person with an anxiety disorder, on the other hand, might feel too anxious.
Research has linked genes that regulate the daily cycle of wakefulness and sleepiness — known as circadian clock genes — to particular psychiatric disorders, including bipolar disorder, seasonal affective disorder, and schizophrenia.
Continual misalignments between a person’s internal “clock” and their actual sleeping pattern may contribute to their vulnerability to these conditions.
Interestingly, scientists have yet to find any association between circadian clock genes and major depression. However, several lines of evidence implicate a sleep stage known as REM sleep.
After you fall asleep, your brain enters three progressively deeper stages of non-REM sleep, which is mostly dreamless. After about 90 minutes, it enters REM sleep, which is when most dreaming occurs.
Normally, the brain will cycle through these stages several times in the course of a night’s sleep, with the REM stages getting progressively longer.
However, people with major depression tend to enter their first REM sleep stage more quickly than usual after falling asleep, and it lasts longer.
Research suggests that we process emotional memories during healthy REM sleep, helping us “unlearn” frightening or painful experiences.
Els van der Helm and Matthew Walker, sleep scientists at the University of California, Berkeley, have speculated that the normal pattern of emotional processing that occurs during REM sleep breaks down in people with depression.
So rather than helping them unlearn negative associations, these memories somehow become consolidated during their REM sleep. Over time, this contributes to an increasingly bleak mindset.
In support of their hypothesis, the researchers note that many antidepressants suppress REM sleep, which may steadily improve mood by preventing this consolidation of negative emotional memories from happening.
Interestingly, in some people, total sleep deprivation can rapidly lift depression, though only temporarily. Van der Helm and Walker believe that this may work in much the same way as the antidepressants — by depriving the brain of this dysfunctional type of REM sleep.
Problems with REM sleep also appear to play a role in post-traumatic stress disorder (PTSD).
In the recurrent nightmares that people with PTSD typically experience, it is as though the brain is repeatedly trying and failing to remove the emotional label associated with the memory of a traumatic event.
A review of research suggests that the drug prazosin, which doctors usually prescribe for high blood pressure, can relieve the nightmares of military combat veterans with PTSD.
The drug seems to do this by lowering levels of noradrenaline, which is one of several brain hormones that determine our progression through the different stages of sleep as their levels change.
Noradrenaline suppresses REM sleep. By reducing the hormone’s concentration in the brains of veterans with PTSD, prazosin may promote more effective REM sleep, which then erases the emotional label that is causing their recurrent nightmares.
This year, psychiatrists in the Netherlands have launched a major investigation of sleep problems in people with newly diagnosed mental health conditions, including bipolar disorder, depression, anxiety, PTSD, and schizophrenia.
As well as assessing the incidence and nature of sleep difficulties in people with these conditions, the researchers will randomly assign participants with sleep problems to receive either their usual care or treatment at a sleep clinic.
Describing their forthcoming study in the journal BMC Psychiatry, the psychiatrists write:
“Despite a high occurrence of sleep disorders and established negative effects on mental health, little attention is paid to sleep problems in mental health care. Sleep disorders are frequently diagnosed years after onset; years in which poor sleep already exerted detrimental effects on physical and mental health, daytime functioning, and quality of life.”
If successful, their clinical trial will provide hope that there is a way to slow down or even prevent the vicious cycle of poor sleep quality and worsening mental health.
