Have you ever sat with your doctor and looked something up together on the internet? No? Just me? In this article we discuss a paper published that ranked and summarised findings on what we will call, for now, the relationship between circadian rhythm and mental health. One of the topics frequently raised by patients, which doctors rarely discuss and seem to know little about. But it is getting more airtime in research.
People talk about how they seem to feel better or worse depending on seasons, time of the day, menstrual cycle or day of the week. Described here before as “the rhythm of wellbeing”, what scientists would call chronobiology, the body’s internal biological clock, and its impact on mental health. Research in this area is advancing. For example, we have recently featured blogs about the use of wearable and digital devices to anticipate relapse in depression and bipolar, and a study of research priorities in the area.
Building on this growing body of work, Crouse and colleagues set out to develop expert consensus about what it is important for clinicians to know about the chronobiology and chronotherapy specific to bipolar disorder, where the hypothesis of a core role of circadian rhythms in bipolar disorder is now widely accepted (McCarthy et al., 2022). Despite this a prior review of 25 practice guidelines found that less than half discussed circadian disturbances (Flint et al., 2022). It gets worse, 409 medical schools in 12 countries were surveyed on the amount of time spent on sleep education during their medical studies and they said they spent less than 3 hours on it. With a quarter of those institutions never touching this topic at all.
Methods
It was based on this context that a research team of 30 experts from 15 countries in Europe, North and South America and the Asia Pacific was put together with the mandate to compile statements for inclusion in practice guidelines for clinicians and medical schools particularly mental health departments.
The experts engaged in a Delphi study, which is a study by experts and, in this case, for experts and medical practitioners, where the participants seek to reach consensus. Here they sought to agree on the essential information about chronobiology and chronotherapy that clinicians need to give the best care to people with bipolar disorder.
Results
The team extracted 960 statements from research papers and grey literature on chronobiology and chronotherapy, and experts rated 837 statements over three rounds. A statement reached consensus if at least 80% of experts rated it essential or important. In the end, 342 statements reached consensus, and they were grouped into four themes.
Basic Circadian Science
The first theme by which statements were assessed and then ranked was Basic Circadian Science. Essentially, they agreed on 70 statements that captured the knowledge clinicians should have adequate access to. They captured that clinicians should know that external stimuli trains a person’s rhythm, that some people are “night owls” while others are “morning larks” and that melatonin is suppressed by light and that it is in fact a chemical signalling darkness and not a sleep hormone (as commonly believed).
Circadian Health and Disruption
The second theme was Circadian Health and Disruption. Here they agreed on 42 statements relating to the knowledge and implementation of the importance of morning light exposure and decreasing light exposure in the evening to ensure that the biological clock is on time and to mitigate ‘social jetlag.’ And that a sleep-wake cycle that is all over the place is associated with mood instability. In summary, here they captured two main ideas, that medical practitioners should know what disrupts circadian rhythms and how people living with bipolar disorder can minimise those disturbances and then that medical practitioners should have access to the principles that can help them predict their patient’s illness trajectory depending on the existing external and related circadian lifestyle factors.
Chronobiology of Bipolar Disorder
The third theme was the Chronobiology of Bipolar Disorder. Here they had 73 statements specific to chronobiology among people with that diagnosis, plus 11 on assessing circadian rhythms in clinical practice. For example, that the relationship between bipolar disorder and sleep is bi-directional and so sleep disturbances may cause bipolar disorder symptoms, while bipolar disorder may cause sleep disturbances. And that sleep disturbances tend to endure whether one is in an episode or not.
Chronotherapies
The fourth and final theme was Chronotherapies. Here they agreed on six major affective chronotherapies that medical practitioners with sufficient training and the correct equipment could then intervene with. These were bright light therapy, wake therapy, dark therapy, interpersonal and social rhythm therapy (IPSRT), cognitive behaviour therapy for insomnia adapted for bipolar disorder (CBT-I-BD), and then melatonin and melatonergic agonists. Although on melatonin and melatonergic agonists, the jury is still out on whether they work because there is a lack of evidence.
A complete list of consensus statements is shared on the Open Science Framework. They are easy to find, read and understand. You are encouraged, by the authors of the original paper, to check them out as you update the guidelines and curricula.
Conclusions
The authors conclude:
An expert consensus was obtained on the essential information about the chronobiology and chronotherapy of BD (bipolar disorder), intended to help clinicians optimise their management of BD. Dissemination of this knowledge is expected to enhance the training and efficacy of clinicians.
Strengths and limitations
I noted that some of the authors of the paper are known proponents of some chronotherapies mentioned in the paper, and I would like to congratulate the team in including so many authors and reviewers who could counter any slant that might have occurred due to biases from investigator allegiances.
Notable limitations that need highlighting are:
- There were no participants from (Africa) and then also from the two most populated countries (China and India)
- There were very few participants from countries with circadian challenges that are unique to them such as those who experience polar nights
- Lastly, medical practitioners who also care for persons living with bipolar disorder, but who are not psychiatrists (e.g. psychiatric nurses) did not feature prominently in the study.
Due to how experts were recruited (snowball sampling) this could explain why the experts mainly came from areas highly represented within the International Society for Bipolar Disorders (ISBD), furthermore, it begs the question, “how likely is my colleague to have a view very different from mine on the preferred adjunct bipolar disorder management practices?”
Implications for practice
Overall, the findings in this paper highlight the urgency of sufficiently including chronobiology and chronotherapy knowledge in medical education, particularly in the psychiatric education and training. It also highlights the importance of educating patients on chronobiology and chronotherapies so that they are empowered to participate in their own health care. The hope is that this will improve mood stability and long-term outcomes for people living with bipolar disorder, although this study didn’t test that.
As stated earlier, the paper already encourages readers to “use the full consensus body of information in their own educational and training programs and curricula”, while the research team works on disseminating the findings and guidelines.
I would recommend that in the dissemination of the resultant guidelines to countries not represented in this study, that some professional caution/respect should be exercised, encouraging researchers within those communities to review and adapt the findings for local implementation. Members of the Pan African Chapter of the ISBD may be invited to participate in the writing of the practice notes that will be disseminated. The same members can verify, through a shorter study, whether chronobiology and chronotherapies receive little attention in training institutions in Africa as well without making assumptions. And then doing the same for India, China and countries with polar nights.
This study highlights the need to actively drive ISBD chapters in India and China. Funding for such studies is limited and infrequent, if an opportunity arises to conduct such a study, every attempt should be made to include as varied a people as possible.
On a different note, in the days of Artificial Intelligence, internet of things and wearables, chronotherapies create opportunities for technology development relevant to the management of bipolar disorder, it provides for the quick implementation of individualised healthcare, continuous access to reliable client data and the ability to scale this type of care, which show promise.
Next time my doctor and I are searching the internet for what I just brought up with them in the consultation, I will appreciate that very few practitioners are trained in these, and those who received training were insufficiently trained and that practice guidelines follow the same trend. For medical teams based in Africa, I need to be extra lenient because geography plays a role since many ground-breaking studies tend to not feature African based medical practitioners and African based persons with lived experience.
Statement of interests
Nomhle Nhlapho is based in South Africa. She is a regular attendee on IPSRT training and discussion webinars. She also sits on two LEAP teams that are under Dr Daniel J Smith at the University of Edinburgh. She is also a member of the Pan African Chapter of the ISBD.
Edited by
Simon Bradstreet.
Links
Primary paper
Jacob Crouse, Victoria Loblay, Anthony Jorm, Timothy Wong, Zsofi de Haan, Carla Gorban, Mirim Shin, Emiliana Tonini, Chris Aiken, Lauren Alloy, Kürşat Altinbaş, Serge Beaulieu, Joanne Carpenter, Bruno Etain, Yuichi Esaki, Jess Fiedorowicz, Corrado Garbazza, Pierre Geoffroy, Bartholomeus Haarman, Tone Henriksen, Maria Paz Hidalgo, Maree Inder, Raymond Lam, Helle Madsen, Colleen McClung, Gunnar Morken, Laura Palagini, James Phelps, Richard Porter, Aswin Ratheesh, Rixt Riemersma-Van der Lek, Janusz Rybakowski, Erika Saunders, Peter Schulte, Daniel Smith, Holly Swartz, Bryan Tolliver, Anna Wirz-Justice, Ian Hickie, John Gottlieb & the Chronobiology & Chronotherapy Task Force of the International Society for Bipolar Disorders. (2026) Chronobiology & Chronotherapy Task Force of the International Society for Bipolar Disorders. Essential Information About Chronobiology and Chronotherapy for the Optimal Care of People With Bipolar Disorders: An Expert Consensus. Bipolar Disord. 2026 Aug;28(5)
Other references
Flint T, Hennion V, Etain B, Scott J. Short communication: Do clinical guidelines for bipolar disorders adequately address sleep, circadian rhythm, activity and lifestyle problems? J Affect Disord. 2022 Mar 15;301:433-436.
McCarthy MJ, Gottlieb JF, Gonzalez R, McClung CA, et al. Neurobiological and behavioral mechanisms of circadian rhythm disruption in bipolar disorder: A critical multi-disciplinary literature review and agenda for future research from the ISBD task force on chronobiology. Bipolar Disord. 2022 May;24(3):232-263. doi: 10.1111/bdi.13165. Epub 2021 Dec 10. PMID: 34850507; PMCID: PMC9149148.
