A new study of adolescents in Finland reported links between various indicators of circadian rhythms and psychiatric disorders. Namely, suicidality was linked with later sleep midpoint, irregular sleep, and delayed sleep phase. People with severe depression had longer circadian periods, while a preference for eveningness was linked to generalized anxiety, panic disorder, and a number of other problems. The study was published in the Journal of Psychiatric Research.
Circadian rhythms are near 24-hour cycles that are part of the body’s internal clock. They regulate a number of bodily functions and mental well-being. Functions such as body temperature, secretion of certain hormones, but also our sleep and wake cycle are all regulated by the circadian rhythms of the body.
Circadian rhythms have also been associated with certain psychiatric illnesses. For example, depression, scientifically known as the major depressive disorder, is thought to be associated with disruptions in sleep timing and internal circadian rhythms. Apart from depression, a number of other psychiatric disorders have been known to be accompanied with sleep problems.
The age of life when most psychiatric disorders start is adolescence. It is also a period when circadian rhythms begin to transform. Psychological, social, and biological pressures toward activities later in the day and at night delay the time when adolescents go to sleep, paving the way for problems in circadian rhythm regulation. But is there a connection between properties of circadian rhythms and psychiatric illnesses in adolescence?
To answer this question, Liisa Kuula and her colleagues from the University of Helsinki in Finland analyzed data from a group of participants of the “SleepHelsinki!” study who were born in 1999 and 2000. Measurements and assessments used in the study were collected in 2017 and 2018, when participants were around 18 years of age.
Based on an online survey, the study authors identified a group of adolescents who reported going to sleep after 1 am at least three times per week and those who did not. Of these, 342 agreed to participate in the study (238 females), but researchers obtained complete data from 262 participants only.
In the scope of the study, participants were interviewed using the M.I.N.I. International Neuropsychiatric Interview to identify current and lifetime psychiatric symptoms. They were then asked to carry an actigraphy device (GeneActiv Original) and a temperature logging device (Thermochron iButtons) for 7 days.
The devices were mailed to them with detailed instructions on how to use them. The actigraphy device is worn on a wrist (like a watch) and it logs the movements of the participant’s hand. These movement data are used to make inferences about a person’s sleep characteristics.
The temperature logging device was also worn on a wrist and set to record the body temperature of the participant’s wrist every minute. These temperature data were used to establish the circadian period length based on body temperature change patterns.
Based on actigraphy measures, the researchers estimated sleep duration of participants (total sleep time), sleep quality (percentage of actual sleep after falling asleep), sleep timing (the midpoint of the sleep period) and sleep regularity (how much the sleep duration and the midpoint of sleep varied). Participants also completed an assessment of circadian preference (the Morningness-Eveningness Questionnaire) and were divided into morning, intermediate and evening groups based on the results.
Results showed that psychiatric disorders were more common in females than in males. Females were more likely to suffer from severe depression, social anxiety and multiple disorders at the same time. Females also slept 22.3 minutes longer on average than males, the midpoint of their sleep was 28.2 minutes earlier than that of males and they had 2% higher sleep efficiency. Males were more likely to go to sleep later and wake up later (so-called – delayed sleep phase) and their temperature varied less during the day.
When links between psychiatric illnesses and circadian rhythm elements were examined, results showed that people with severe depression had longer circadian period lengths.
“Suicidality was associated with 0.54 h later sleep midpoint, greater sleep duration irregularity, and sleep timing irregularity. Those with manic episodes had greater sleep timing irregularity and those with agoraphobia slept for longer. Those with psychotic symptoms also had greater irregularity in their sleep timing. Comorbidity [having multiple psychiatric illnesses at once] was also associated with later sleep midpoint and sleep timing irregularity,” the researchers wrote.
“We found that sleep regularity and timing reflect wellbeing better than sleep duration. Furthermore, several genes controlling circadian rhythms (such as CLOCK, CRYs, and PERs) have been shown to play a part in the pathophysiology of nearly all psychiatric disorders. Thus, it is likely that circadian patterns represent the neural substrate of mental wellbeing from a genetic, molecular, neurohumoral (i.e. HPA axis and melatonergic system), and behavioural level,” they concluded.
The study sheds light on the connection between circadian rhythms and mental health. However, it also has limitations that should be taken into account. Namely, it did not use actual diagnoses of mental illness from medical records, but relied on self-reporting of symptoms. There was a substantial overlap between participants with depression and suicidality. Additionally, the quality of sleep assessments based solely on actigraphy is limited.
The study,“Adolescent circadian patterns link with psychiatric problems: A multimodal approach”, was authored by Liisa Kuula, Risto Halonen, Jari Lipsanen, and Anu-Katriina Pesonen.
