Sleep disorders, anxiety, and depression are widespread and a growing problem among the younger population.
But why is our sleep and mental health in such poor shape, and why does it seem so difficult to improve the situation?
A new study from the University of Copenhagen aims to shed further light on these questions.
In a new study, researchers map how a range of biological, psychological and social factors, including stress, screen habits and smoking, interact to create self-reinforcing cycles that put young adults at risk for poor mental health.
We know that sleep deprivation and depressive symptoms often go hand in hand, but mapping allows us to better understand how a variety of other mechanisms potentially perpetuate the problem. This gives us a more nuanced picture of why it is so difficult for young people to break out of these self-reinforcing ‘vicious cycles’. ”
Jeroen Uleman, Assistant Professor, Copenhagen Center for Health Complexity
complex public health crisis
In this study, researchers mapped how 29 factors interact with each other in young adults aged 18 to 40.
This model shows how sleep disturbances worsen symptoms of depression, which in turn affects sleep, and how factors such as stress, screen habits, physical activity, social relationships, nicotine use, and inflammation in the body participate in various self-reinforcing loops.
“For example, our model shows how smoking can cause symptoms of depression, and how those symptoms can interfere with sleep. While you might smoke more to counter increased fatigue, nicotine can affect your sleep quality, again worsening your symptoms of depression. The other loop is even more complex,” says Jeroen Eureman.
This complexity is exactly what needs to be unraveled, said Nadja Hrubey-Rod, professor of epidemiology and co-author of the study.
“Rather than focusing solely on a single cause of the growing sleep and mental health crisis among young people, such as smartphone use or the way the school system is structured, our research shows that many factors are at play, and that these factors are tightly intertwined in a complex network that we need to understand to understand how to break the self-reinforcing cycle,” she says.
Experts identify important connections
The researchers invited 14 experts in fields such as sleep research, psychology, sociology, epidemiology, and biology to build the model by proposing key factors, assessing causal relationships between them, and highlighting scientific literature supporting the association.
So far, the experts and researchers behind this study have identified 175 causal relationships between individual factors and thousands of potential self-reinforcing loops.
However, the researchers stress that many ‘vicious cycles’ have not been empirically investigated and more research is needed to understand their effects.
Also, this model should not be considered an exhaustive explanation of sleep and mental health in young people. Rather, researchers consider it a living tool that can be continually updated with more elements from additional fields such as political and environmental aspects, and that can be further supported and expanded through additional research.
Support local interventions
This model can help highlight potential areas for intervention, such as local authorities responsible for strengthening local public health, including mental health, through upcoming public health legislation.
Now, the Copenhagen Center for Health Complexity at the University of Copenhagen, led by Nadja Hrvej-Rod, is partnering with the city of Värborg-Midfinn to improve the health of children and young people, including during sleep, where this model has come in handy.
“Workshops with municipal practitioners have already taken place, in which we provided input from the model. This way, decisions can be made based on both practical experience and scientific evidence. Our hope is that this model can be used in the political decision-making process of municipalities across the country when the public health law is implemented,” said Nadja Hruvej Rod.
The City of Fabolg-Midfin is also excited about this collaboration.
“Our collaboration with the Copenhagen Center for Health Complexity at the University of Copenhagen provides us with expert evidence that can be compared with our experience in municipalities. In this way, our partnership with researchers will help , prompting us to identify where it makes sense to intervene now and in the long term. Furthermore, it is very meaningful that the general insights generated through collaboration can benefit everyone,” said the Mayor. Anstina Krog, City of Fabolg Midfin.
About research
This research identifies a number of self-reinforcing cycles that can trap young people in psychological distress and poor sleep patterns.
This loop consists of 29 factors and 175 causal relationships spanning biological, psychological behavioral, and social dimensions, such as associations between smoking, sleep disorders, physical health, loneliness, and socio-economic status.
Although this model is based on expert knowledge and existing literature, there has been no systematic review of all 175 causal relationships or empirical studies of each loop. Further research is needed to understand the public health implications of the loop.
Expert-driven approaches also carry the risk of subjectivity and the potential for over-representation of certain areas. Finally, this model does not cover all possible influences on sleep and depressive symptoms, such as environmental and political factors.
Therefore, although this model does not provide an exhaustive account of sleep and mental health issues in young people, it should be seen as a ‘living tool’ that should be continually updated and used to inform policy processes.
sauce:
Reference magazines:
Uleman, J.F.; others (2026). The young adult sleep model: An evolving causal loop diagram of mental health dynamics. BMC Medicine. DOI: 10.1186/s12916-026-04738-7. https://link.springer.com/article/10.1186/s12916-026-04738-7.
