Disturbed sleep and depression have a complicated relationship. Frederick Snyder, one of the pioneers of research on sleep in mental disorders, phrased it this way: Troubled minds have troubled sleep, and troubled sleep leads to troubled minds. Indeed, about three-fourths of persons with major depression describe poor sleep, often awakening early, but also difficulty going to sleep or awakening unrefreshed in the morning. When sleep researchers began to make brainwave recordings of depressed persons in the laboratory, they found that their sleep was short, shallow, and fragmented, as well as having changes in the timing of rapid eye movement REM sleep. Let’s look a little at what each of these means.
Short and shallow: In addition to getting less total sleep, persons with major depression have less slow-wave deep sleep. This is a deep part of sleep thought to be important in the restorative properties of sleep.
Fragmented: There are many brief arousals during the night. Sometimes these are so short that a person doesn’t remember the individual events, while others are long awakenings disrupting the night. This is important because the continuity of sleep— continuous sleep without interruptions— may be as important to feeling refreshed as the total amount of sleep one gets.
REM sleep phenomena: REM sleep, during which most dreaming occurs, and which may be involved in memory processing, emotional balance and many other activities, changes during depression. During REM sleep, as its name indicates, there are rapid movements of the eyes. In depression, these are particularly intense during the first REM episode of the night (there are usually four or five such episodes, usually separated by roughly 90 minutes). Typically, the first REM episode occurs about 90-110 minutes after sleep onset. In depressed persons, however, it often appears much earlier, often 60-80 minutes after falling asleep. This has led some researchers to believe that there are abnormalities of the body’s rhythms which may potentially play a role in depression.
There are many other theories of the association of poor sleep with depression. Another notion is that in depression, there is a defect in the normal mechanism by which one becomes more sleepy the longer one stays awake (the ‘homeostatic process’). Another, suggested by Frederick Snyder, was that there is a sequence of events: an upsetting event happens to a person, resulting in decreased REM sleep, which in turn leads to depression. In retrospect, this seems less likely, as the REM changes usually occur very close to the onset of depression, and later research has indicated that purposely depriving a person of REM sleep can actually be a treatment for depression.
Interestingly, it has been found that purposefully keeping a depressed person up all night may result in a rapid improvement in mood, which may be as effective (and more rapid) than most antidepressants. Later work indicated that similar results could be found by partial sleep deprivation (for only half the night) or, as we mentioned earlier, by selectively depriving a person of REM sleep. These treatments are not very practical, and also have limitations (in persons with bipolar illness, they may lead to new manic episodes), but they make an interesting point: sleep disturbances may not just be a result of depression, but in addition some dysfunction of sleep mechanisms may be involved in the genesis of depression. Exploring this two-way relationship is an ongoing and active area of sleep research, which holds the promise of finding new ways to understand depression.
Author: Wallace B. Mendelson MD
Dr. Mendelson’s recent books include ‘Understanding Antidepressants’ and ‘Understanding Sleeping Pills’, both available at Amazon.
© 2021 American Sleep Association.