Circadian subtype of depression

Key Findings of the Study

Prevalence: About 23% to 25% (2,604 participants) of individuals with depression met the criteria for the circadian subtype. 

Classification Criteria: Participants needed to exhibit at least three of six binary circadian features:

Social jetlag (significant shift in sleep schedule between work/free days)
Seasonality
Delayed sleep midpoint
Evening chronotype ("night owl" preference)
Sleep inertia (severe morning tiredness)
Hypersomnia (sleeping longer during depressive episodes

Genetic and Biological Correlates

Using polygenic risk scores (PGS), researchers found that the circadian subtype shared higher genetic loading with: 

Mental and neurodevelopmental disorders: Major depressive disorder, bipolar disorder, and attention-deficit/hyperactivity disorder (ADHD).
Sleep-wake traits: Delayed sleep midpoint, insomnia, and evening chronotype.
Metabolic and inflammatory markers: Higher body mass index (BMI), triglycerides, insulin resistance, and interleukin-6 (IL-6).

Ref: Clinical and genetic correlates of a circadian subtype of depression in the Australian Genetics of Depression Study

Published online by Cambridge University Press:  20 October 2026

Ayurveda Day 2026 - Ayurveda for Healthier Tomorrow

https://ayurvedaday.org.in/

September 23 coincides with the autumnal equinox, when day and night are of nearly equal length. This astronomical balance symbolizes nature's equilibrium, reflecting Ayurveda's core philosophy of achieving harmony and balance within the mind, body, and spirit.

Traditionally Ayurveda Day is celebrated on Dhanvantari Jayanti (Dhanteras). But through Gazette Notification issued in March 2025, Govt. of India decided to celebrate Ayurveda Day on 23rd September every year.

Ayurveda and Chronobiology are having many similarities. Ayurvedic concepts may be better explained to modern world through chronobiological terminologies. 

We have coined a novel term 'ChronoPrakriti' which is the combination of chronotype and Prakriti type. For more information please check https://chronoprakriti.com/.

Chronobiology conferences in India in 2026

International Conference on “Biological Timekeeping Across the Tree of Life: From Ecology to Human Health,” being held in conjunction with the 33rd Biennial Meeting of the Indian Society for Chronobiology (InSC), from 19–21 December 2026 at the School of Biology, IISER TVM, Kerala. The conference will bring together eminent scientists, academicians, researchers, and students to discuss recent advances and emerging trends in chronobiology and its interdisciplinary applications.

https://nishankannan.wixsite.com/cblab

https://chronobiologyindia.org/

National Symposium on Chronobiology – Integrating Multidisciplinary Perspectives and Applications, being organized by the School of Studies in Life Science, Pt. Ravishankar Shukla University, Raipur, from November 26–28, 2026.

https://www.prsu.ac.in/academic-departments/utd-departments/School-of-Studies-in-Life-Science/6 

nsc2026raipur@gmail.com

Light exposure and sleep architecture in real-world settings

Light exposure can influence sleep timing, quality, and architecture, yet evidence from real-world settings remains limited. We investigated personal light exposure, quantified as melanopic equivalent daylight illuminance, and sleep parameters using consumer-grade wearables in a convenience sample of UK adults (n = 89). Participants simultaneously wore light sensors and sleep trackers for 7 days, yielding over 500 days of data, complemented by daily sleep diaries. Earlier sleep/wake timing was associated with longer-duration daytime light exposure, as well as more regular, less fragmented light patterns across the week. Higher interdaily stability and lower intradaily variability of light exposure were further linked to enhanced deep sleep intensity during the initial portion of the night. Subjective and wearable-derived measures were generally correlated, although disrupted sleep architecture was associated with greater discrepancies between subjective and wearable sleep estimates. These findings demonstrate the feasibility of naturalistic protocols and highlight the potential importance of brighter days and more stable, less fragmented light exposure patterns for sleep.

Akgun, S.G., Gemici, B., Roddis, C. et al. Light exposure and sleep architecture in real-world settings. npj Biol Timing Sleep 3, 30 (2026). https://doi.org/10.1038/s44323-026-00087-z

World Circadian Day

World Circadian Day is celebrated globally on June24th. Sponsored by the Society for Research on Biological Rhythms (SRBR), the event raises awareness about how our internal body clocks regulate sleep, metabolism, and overall health.

Zero Shadow Day - Outcome of Geophysical cycles, basis of Biological rhythms

A Zero Shadow Day (ZSD) is an astronomical phenomenon where the Sun is directly overhead (at its zenith), causing vertical objects to cast no shadow at local noon. This event is entirely driven by the geophysical cycle of Earth's revolution around the Sun and its axial tilt, occurring strictly within tropical latitudes.

Key Geophysical Drivers

• Earth’s Axial Tilt (23.5 degrees): The primary cause is the (23.5 degrees) tilt of Earth's rotation axis relative to the plane of its revolution around the Sun.
• Apparent Movement of the Sun (Uttarayan & Dakshinayan): As the Earth orbits the Sun, the Sun appears to move north and south across the sky between 23.5 degrees N (Tropic of Cancer) and 23.5 degrees S (Tropic of Capricorn) over a year.
• Declination Matching Latitude: A zero shadow day occurs when the declination of the Sun matches the latitude of a particular location

Frequency and Timing

• Occurrence: The phenomenon happens twice a year for any location within the tropics (between \(\pm 23.5^{\circ }\) latitude).
• Timing: One event occurs during the northward movement of the sun (Uttarayan, March–June) and the other during the southward movement (Dakshinayan, July–September).
• Duration: The event is extremely brief, lasting only a few minutes or seconds, and occurs exactly at local noon.
• Location Constraints: Outside the tropics (>23.5 latitude), the Sun is never directly overhead, so zero shadow days do not occur.

Ref: https://astron-soc.in/outreach/activities/zero-shadow-day/

Chronobiology Connect: Open forum for like minded people interested in Circadian Biology

We are pleased to invite you to the upcoming Chronobiology open forum, 'ChronoConnect', a platform dedicated to exploring the fascinating science of biological rhythms and their impact on health, medicine, and research. The event aims to bring together researchers, academicians, and students to share knowledge, ideas, and recent advancements in the field of chronobiology.

In addition to the meet, we are delighted to announce that a newsletter titled “ChronoPrakriti” will be published as part of this event. We warmly invite you to contribute articles, short communications, or insights related to chronobiology, circadian rhythms, integrative health, or allied areas.

Submission Deadline: 24/04/2026

This is a great opportunity to showcase your work and be a part of an engaging academic initiative.

Event Details:

• Date: 25/04/2026
• Time: 04:00 PM
• Venue: SPM's Prin B V Bhide Foundation for Research, Innovation and Incubation, Pune
• Location: https://maps.app.goo.gl/aQFYEuy6LDyxcxQr6

You are also invited to join our community using the link below and kindly share it with others interested in chronobiology:
Join the Community via: https://forms.gle/ZvYytawV7nr7ugog9 

We look forward to your active participation and valuable contributions.

For more details:

Email: spm.bhidefoundation@gmail.com

Phone: 8421479820