�鶹��

The clock display shows 3:32 AM. The night is pitch black, an owl hoots from the top of a tree, and the neighbours’ windows are dark — except for those who also can’t sleep. And there are more and more of them. Sleep problems are widespread and growing.

A new Danish study, supported by the Lundbeck Foundation and published in Science Advances, shows a significant increase over time in the proportion of young and adult Danes aged 15 to 45 who say they have experienced sleep problems. In 2010, the percentage was 34%. Eleven years later, in 2021, 49% had experienced poor sleep.

But what’s behind the sleeplessness? Why have the researchers focused on this particular age group? And what do they hope their study will contribute? We asked two of the researchers behind the study: Professor of Epidemiology Naja Hulvej Rod and Assistant Professor Adrian G. Zucco from the Center for Complexity and Health at the University of Copenhagen.

Sleep problems can be a sign of mental strain

When researchers zoom in on why Danes lie awake at night, tossing and turning, it’s because sleep isn’t “just” about sleeping.

“I’ve studied sleep for more than 15 years, and it interests me because sleep problems are a core symptom of a wide range of conditions such as depression, anxiety, and stress,” says Naja Hulvej Rod.

“Sleep problems can be an early indicator of mental strain. And we’re seeing a growing prevalence of mental health issues, stress, and poor well-being, especially among young people. That was one of the main reasons we launched a larger research project, of which this study is a part.”

Naja Hulvej Rod also explains why the researchers focused specifically on the 15–45 age group:

“Sleep is fundamental to our health and well-being at any age, but there aren’t many studies focusing on this age group. Yet the transition to adulthood, entering the workforce, establishing oneself, and starting a family, is a significant period. Not only for the individual but also for society, because this is when people contribute most, both at home and at work. So there’s a knowledge gap we want to fill.”

Self-reported sleep problems

The data used in the study covers self-reported sleep problems, ranging from a single episode of poor sleep within 14 days to severe disturbances every night for two weeks. The researchers wanted to include all types of sleep issues.

“For us, it was important to acknowledge any type of self-reported sleep problem. But we also want to emphasise that not everyone who experiences sleep problems has a condition that requires treatment,” says Adrian G. Zucco.

In the study, researchers compared data on sleep problems with prescriptions for sleep medications and diagnoses of sleep disorders that require treatment. They did not find an increase in diagnoses corresponding to the rise in reported sleep problems, but they did find a tenfold increase in the use of the sleep hormone melatonin over eleven years. At the same time, there was a decline in the use of stronger sleeping pills, such as benzodiazepines. This suggests that some people are switching from stronger to milder substances. Still, the high use of melatonin is concerning.

“Melatonin is recommended for people over 55, but not for this younger age group. The official treatment recommendation for sleep problems among young and younger adults is cognitive behavioural therapy. So, this result raises questions about whether they’re actually being offered that. It’s something worth looking into,” says Zucco.

Surprisingly many causes

Mobile phones are often cited in the media as the reason for young people’s sleep problems. And the researchers at the University of Copenhagen are actually investigating the connection between phones and sleep in another study, but in this one, they found a range of other possible causes. Naja Hulvej Rod warns against focusing on single explanations.

“We risk overlooking important connections if we only look at one factor. That’s why we chose to zoom out and get the bigger picture — to study how sleep problems have evolved over time and how the different causes interact. And even though I’ve studied this for many years, I was still surprised by the complexity. I hadn’t expected so many variations of sleep problems and so many different related conditions.”

In their analysis of prescriptions, the researchers found a possible link between sleep problems and both mental disorders and pain, since medication for depression, anxiety, or pain is often prescribed alongside sleep medication. Certain types of strain during childhood also appear to be related to sleep problems later in life. This includes having a sibling with a mental illness, being placed in foster care, and experiencing parental divorce. These kinds of challenges are particularly associated with so-called non-organic sleep problems issues linked to the mind rather than the body, such as difficulty falling asleep due to racing thoughts or emotional distress.

Social factors can also be connected to sleep disturbances, and the study shows a clear link with childhood poverty. In these cases, the issues are organic sleep disorders; those caused by physical or medical conditions, such as sleep apnea, epilepsy, or hormonal imbalances.

The study will be followed by additional research to confirm or refute some of the relationships the researchers have identified.

“We now have a range of possible causes from which we can form hypotheses and investigate further,” says Naja Hulvej Rod.

In particular, the researchers want to study the less well-explored connections, explains Adrian G. Zucco:

“There have been many studies that only look at medical factors, and I think our study highlights the importance of viewing sleep problems in the context of socioeconomic and social aspects, which also affect people.”

With this research, the two scientists hope to raise awareness, both among fellow researchers and the general public, about the many facets of sleep problems, and specifically about sleep issues in young and younger adults.

“I belong to the younger age group myself, and I hope we can help make it more acceptable to talk about sleep problems. Conversations about sleep can also open the door to conversations about mental health, because the two are often connected,” says Adrian G. Zucco.

If anything can keep a sleep researcher awake at night, it’s the thought that sleep research might cause unnecessary worry, adding to people’s sleeplessness. That’s why it’s important for Naja Hulvej Rod to emphasise:

“People reading about our study shouldn’t be afraid if they’re sleeping poorly for a while. It’s completely normal to have occasional trouble sleeping. That’s not the same as having a sleep disorder that requires treatment.”