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The relationship between sleep and depression is strong—it's a two-way street.
About 3 in 4 people facing depression also experience sleep complaints, primarily insomnia or hypersomnia, which is the sensation of excessive daytime sleepiness. These complaints are present in about 40% of young adults and 10% of elderly patients with depression, mostly women.
Beyond the symptoms that may reflect depression's impact on sleep quality, untreated sleep disorders themselves can be the triggering factor for depression.
This happens because fragmented or insufficient sleep causes poor processing of memories and emotions, leading to mood changes and altered perceptions of how we feel or how others feel about us.
Sleep disturbances are, in fact, one of the diagnostic criteria for depression—that's how strong the relationship is.
People with depression generally experience one or more of the following symptoms:
- Difficulty falling asleep
- Waking up multiple times during the night or earlier than desired
- The sensation of non-restorative sleep
- A decrease in total sleep time
- Disturbing nightmares
- Excessive daytime sleepiness
If you thought sleeping too little was the only problem, think again!
Sleeping too much can also be harmful. And do you know what studies show is very common and an aggravating factor? Even after depression is under control, sleep disorders tend to persist, and this is one of the factors that can trigger relapses.
But why does this happen?
Science increasingly demonstrates the importance of regular sleep patterns, as sleep is a biological rhythm connected to various other physiological functions. Sleep is a rhythm that follows the circadian cycle, the set of bodily changes that occur periodically over approximately 24 hours (circa = about; dian = a day).
This cycle is responsible for synchronizing a series of important functions beyond sleep and wake times—for example, the timing and duration of secretion of most hormones, which regulate our sense of hunger, alertness levels, the production of antibodies and new cells, among other functions.
One of these hormones linked to our ability to stay alert, also known as the stress hormone, is cortisol. People with depression may have elevated cortisol levels, and this is one of the mechanisms through which the mood deterioration characteristic of depression is observed.
Cortisol secretion is directly connected to melatonin secretion, known as the sleep-inducing hormone, as it is one of the main substances linked to synchronizing our biological clock. Therefore, changes in cortisol also alter the timing and duration of when we feel sleepy.
What are the treatment options?
The good news is that, in theory, medications currently exist that can work to improve both sleep symptoms and depression. That's why it's common to see people with insomnia using an antidepressant as treatment, for example.
Some research highlights a rather peculiar "treatment" for those suffering from depressive symptoms: partial sleep deprivation (PSD), which involves restricting the opportunity to sleep. It's not exactly a conventional "treatment," but a strategy seen in various studies as effective when applied as a short-term intervention.
The simplest explanation for why this strategy works is that people with depressive symptoms tend to spend more time resting in bed, whether due to feelings of fatigue and tiredness or difficulty consolidating sleep.
One study in this area, which tested the acute effect of partial sleep deprivation, found that more than 50% of participants showed a significant reduction in cortisol levels and, consequently, an improvement in depressive symptoms.
But exercise caution—if you notice changes in your sleep quality, the best course of action is to seek help from a specialized healthcare professional, especially if you're already in treatment or have received a diagnosis of depression at some point.
Even non-medication interventions can have side effects or unexpected outcomes, and may end up causing more harm than good.
Mental health is serious business and, as we're learning here, is connected to the entire body, so seek professional help whenever you need it.