You are unlikely to be in the best of moods after a lousy night’s sleep. However, a new study suggests that your negative mood may be due to a loss of quality sleep rather than a lack of quantity.
The study, which was published in the journal Sleep, found that persons who had their sleep interrupted regularly for three nights in a row had a much poorer mood than those who had less sleep owing to later bedtimes.
Patrick Finan, an assistant professor of psychiatry and behavioral sciences at Johns Hopkins University School of Medicine in Baltimore, MD, and colleagues say their findings show that sleep disruption is more harmful to mood than sleep deprivation, which could help explain the link between depression and insomnia.
Adults aged 18 to 64 should strive for 7-9 hours of sleep each night, according to the National Sleep Foundation, while those aged 65 and over should aim for 7-8 hours. According to the Foundation, obtaining adequate sleep can help strengthen the immune system, increase productivity, and improve happiness.
However, studies are rapidly demonstrating that sleep quality is equally as crucial as sleep duration. “When your sleep is disrupted throughout the night, you don’t have the opportunity to go through the sleep stages and get the amount of slow-wave sleep needed to feel restored,” Finan explains.
Sleep disruption resulted in a 31% decrease in pleasant mood
In a study of 62 healthy men and women who were randomized to one of three sleep conditions over three consecutive nights in a clinical research suite, Finan and colleagues revealed the effect of interrupted sleep on mood.
One group got uninterrupted sleep each night, another had bedtimes that were postponed, and the third group was awakened eight times during the night.
Polysomnography was used to track each subject’s sleep stages, which records brain waves, blood oxygen levels, breathing, heart rate, and eye and leg movements.
Participants were asked to indicate how strongly they felt good or negative emotions, such as anger or happiness, at the conclusion of each night, which the researchers used to evaluate their mood.
During the first night, there were no variations in mood across groups, but after the second night, individuals in the interrupted sleep group had a 31% reduction in positive mood, while those in the delayed sleep group had a 12% loss in positive mood. After the third night, the reductions remained.
On any of the three days, the researchers found no significant changes in negative mood between the delayed sleep and interrupted sleep groups, showing that interrupted sleep had a greater detrimental influence on good mood.
Insomnia and depression may be linked to poor slow-wave sleep
The researchers discovered that the interrupted sleep group had shorter periods of slow-wave sleep, or deep sleep – the sleep stage believed vital for body repair and maintenance – than the delayed sleep group after analyzing the polysomnography results throughout the three nights.
Insomnia-related quick facts
- Insomnia occurs when a person has difficulty getting asleep, staying asleep, or waking up repeatedly during the night
- Insomnia is only classified as a condition when it causes severe distress or worry, or when it impairs one’s ability to function during the day
- In the United States, it is estimated that 1% of children and 7% of adolescents suffer from insomnia.
Learn more about insomniaInsomnia: What to know
Furthermore, the researchers discovered that in the interrupted sleep group, a lack of slow-wave sleep was substantially associated with a decrease in positive mood, and that disrupted sleep influenced some components of good mood, such as friendliness and emotions of sympathy.
The researchers believe their findings may explain why many people with chronic insomnia, a sleep disease that affects around 10% of the US population, suffer from depression; it could be due to a lack of slow-wave sleep.
“Many people who suffer from insomnia sleep in fits and starts throughout the night, and they don’t get restorative sleep,” Finan explains. “You can understand how difficult it is for persons with persistent sleep difficulties to get deep sleep.”
However, he points out that more research is needed to acquire a better knowledge of the sleep stages that persons with insomnia go through.