2024-03-14 18:58:57
Each cell in our body has a circadian rhythm. Real biological clocks, these rhythms follow a duration approximately equivalent to 24 hours (circadian comes from the Latin circaaround, and dies, day). They are critical for our health and well-being: for example, they influence the sleep/wake cycle, or hormonal regulation.
When our lifestyle does not correspond to the day/night alternation, our circadian rhythm can be disrupted. This is for example the case when we are subject to time difference, or when we work at night. Various factors such as aging, genetics or certain diseases (such as autoimmune diseases and Alzheimer’s disease) may also be associated with long-term disruptions in the circadian rhythm.
Sleep quality and circadian rhythm disruptions may also be good predictors of the onset or relapse of certain psychological disorders, including depression, anxiety, bipolar disorder and schizophrenia. The more severe a person’s disruptions to sleep and circadian rhythm, the worse their mood, which increases their risk of relapse and compromises the effectiveness of their medical treatments.
If this link between disruption of the circadian rhythm and psychological disorders is well established, the reasons why it exists remain largely unknown. The research that I carry out with my colleagues aims to better understand them.
Disturbances associated with mental disorders
Our work not only allowed us to discover that sleep and circadian rhythm disruptions appear to trigger or worsen various mental disorders (including bipolar disorder and depression), but also to identify some of the specific biological mechanisms underlying this link. .
To help highlight them, we reviewed all the research published over the past ten years on mental disorders such as depression, anxiety and psychosis. We have primarily focused our efforts on adolescents and young adults.
We found that the majority of young people diagnosed with a mental health disorder were also prone to sleep problems, such as insomnia (difficulty falling and staying asleep), delayed sleep phase syndrome and decreased daytime alertness. We also found that a third of people with bipolar disorder (and other mental disorders) have a disrupted circadian rhythm, which results in going to bed and getting up later than normal.
Among the mechanisms that might explain the link between these sleep problems and mental health disorders is an increased vulnerability, at the genetic or molecular level, to disruptions in the circadian rhythm.
We also found that the brain activity of some of the people who participated in the work we analyzed may have been altered. The cause is disruption of chemical signaling pathways that can affect sleep and mood. Beyond these problems, other factors can also lead to sleep and circadian rhythm disorders. This is for example the case when we are inappropriately exposed to light (when we do not receive enough natural light during the day, or on the contrary when we are exposed to an excess of artificial light at night ), or when you eat too late in the evening, or during the night.
Excess artificial light at night might be one of the mechanisms causing circadian rhythm disruption.” junpinzon/Shutterstock
It is important to emphasize that most studies to date have only looked at either the effects of sleep on mood or the effects of circadian disruption on mood. These two aspects have very rarely been studied jointly. Indeed, it is more common (and simpler) to assess the quality of sleep than that of circadian rhythms. Future research should address this issue, which is one of the main limitations of currently available studies.
Adolescence, a risky period
Currently, the World Health Organization estimates that one in seven young people aged ten to nineteen worldwide experiences a mental disorder. Among adolescents, depression and anxiety are among the leading causes of illness and disability. Furthermore, among 15-29 year olds, suicide is the fourth cause of death. Failure to manage mental disorders during adolescence can lead to their persistence into adulthood.
Adolescence is a period during which individuals are particularly vulnerable to the risk of developing mental disorders. This is also the time when their sleep and circadian rhythms change. As a result of the changes that occur at puberty, adolescents’ circadian rhythm changes and they fall asleep later, which tends to lead them to go to bed later. But they still have to get up just as early to go to school, college or high school… As a result, their sleep duration is often shorter than required, which can worsen their mental health.
Our work highlights the importance of paying attention to circadian rhythm disruptions in young people, especially with regard to the risk of developing certain psychological disorders. They reveal that it is also necessary, when someone is facing mental health problems, to take into account the sleep and circadian rhythm problems to which they might be exposed. Addressing these issues might be a way to improve the mental health and quality of life of those affected.
Better management of circadian rhythm disorders
Currently, the management of sleep problems (such as insomnia) relies on cognitive-behavioral therapies and the restriction of time spent in bed (in order to reduce the time spent in bed to a duration closer to the actual duration of sleep). These approaches aim to improve sleep quality, however they do not directly address possible problems due to circadian rhythm disruption.
Our literature review suggests that other approaches may prove useful in improving mood and sleep quality, while also aligning circadian rhythms. These include exposure to natural light (and reducing exposure to nighttime light), paying attention to the timing of certain medications, as well as better eating habits and practicing physical activity during the day. However, further research will be necessary to determine the concrete advantages of each of these interventions in real conditions…
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