In this special episode of Light O’Clock, we share snippets from our very first live recording, captured on stage at Buch Wien in Vienna in November 2025.

Host Caro Guidolin and her colleague Marie-Luise Schreiter answer audience questions on chronotype, light exposure, sleep, shift work, and why people feel more tired in winter.

Many people notice changes in mood, energy, and motivation during the dark winter months. In this episode, we explore Seasonal Affective Disorder (SAD) and the broader experience of feeling low in winter and, importantly, what science-backed strategies can help.

We speak to Delainey Wescott about changes in sleep and circadian rhythms in SAD, and chat with Hester Parr and Hayden Lorimer about the Wintering Well project — an initiative that highlights the power of community, shared experiences, and collective coping during the darker months.

Throughout the episode, we discuss practical approaches to winter wellbeing, including light exposure, daily routines, cognitive reframing of winter, and small habits that can make a meaningful difference.

Links and resources:

• Sleep in seasonal affective disorder: https://doi.org/10.1016/j.copsyc.2019.08.023

• Retinal light sensitivity in summer and winter: https://doi.org/10.1016/j.jad.2021.04.084

• Wintering Well resources (Living with SAD project): https://www.gla.ac.uk/research/az/livingwithsad/winteringwell/resources/. Includes: the guidebook Light is a Right: A Guide to Wintering Well, an online course developed by CBT experts, the Wintering Together Toolkit, and the SAD Stories Exhibition.

Timestamps:

(02:24) What is SAD and how is that different from the winter blues?

(05:16) Geography matters: who is affected by SAD?

(06:50) Circadian rhythms and sleep in SAD

(09:38) Light sensitivity in SAD

(11:50) Evidence-based strategies to alleviate SAD symptoms

(17:30) Summary

(18:35) The Living with SAD project

(22:30) Wintering Well Workshops

(25:45) My patch of winter sky, writing a letter to winter, and my kind of winter neighbourhood

(34:00) Winter Well resources created by the workshops

(36:28) The present and future of the Living with SAD project

(39:45) Wrap up and outro

Light O’Clock is going live from Vienna at Buch Wien 2025 on Saturday, 15 November – and this time, you set the agenda for the episode!

Together with Marie Luise Schreiter, we’ll be diving into your questions about how light shapes our brains, bodies, health, and daily rhythms – live on stage.

What have you always wanted to know about light, sleep, or circadian rhythms?

Send us your question through this link: https://form.jotform.com/252533837926365

For our Season 3 finale of Light O’Clock, we dive into a timely and often overlooked issue: light pollution. Artificial light at night has become a constant in modern life — but what are the hidden consequences?

Our guests, Barbara Harding, Travis Longcore and Karolina M. Zielińska-Dąbkowska, bring scientific insight into how nighttime light exposure may affect human health, including possible links to cancer, and how it disrupts wildlife, ecosystems, and natural rhythms. We also explore practical solutions: since we can’t simply switch off the lights, how can we use artificial light more responsibly to protect both ourselves and the environment? We explain the five principles for responsible outdoor lighting created by International DarkSky Association (now DarkSky International) and the Illuminating Engineering Society.

Links and resources

• DarkSky International website: https://darksky.org/

• Ecological light pollution: https://doi.org/10.1890/1540-9295(2004)002[0191:ELP]2.0.CO;2

• Five principles for responsible outdoor lighting: https://darksky.org/resources/guides-and-how-tos/lighting-principles/

• Outdoor artificial light and cardiometabolic risk: https://doi.org/10.1093/aje/kwae269

• Artificial light at night and cancer risk: https://doi.org/10.1016/j.scitotenv.2024.177059

Timestamps

(00:00) What is light pollution?
(02:17) Light at night and circadian rhythms
(05:18) Light at night and cancer risk
(09:35) How light pollution is measured
(16:11) What's the link between light at night exposure and disease risk?
(19:00) Ecological light pollution
(20:50) Effects of light pollution in animals: birds and turtles
(26:00) Artificial light and animals' circadian rhythms
(28:55) Light pollution changing predators-preys dynamics
(32:30) Awareness towards light pollution in different countries
(35:20) Why did we start to use artificial light in the first place?
(40:30) What are the current lighting standards?
(43:00) Different stakeholders involved in outdoor lighting
(47:00) Five principles for responsible outdoor lighting
(55:20) Wrap up and outro

Why do early mornings feel so brutal for teens? In this episode, we explore the science behind teenage sleep and circadian rhythms and why early school start times may be setting students up for failure.

We talk to students from Italy and Germany, and sleep researcher Dr. Anna Magdalena Biller, to understand how biology, not laziness, is behind teen sleep struggles — and what schools, parents, and teachers could do about it.

Big thanks to Margha, Lea, Giulia, Alice and Viola for sharing their perspectives on school start times!

Links and resources related to the episode’s content:

• Review: Adolescent sleep & school timing

• Meta-analysis: School start times and academic achievement

• Flexible school start study (Germany)

• Expert report for Belgium (only in German)

Timestamps

(00:00) Intro & questions to teenagers

(04:15) Circadian rhythms and sleep in adolescence

(10:15) Consequences of sleep deprivation for teens

(12:28) Initiatives aimed at delaying school start times

(14:48) Studies on changing school start times

(16:55) How do these studies measure sleep?

(19:48) Is changing school start times beneficial for teens?

(26:40) Challenges with implementation in schools

(30:35) What other solutions can we use?

(39:50) Outro

Today, more and more children around the world are developing myopia, or nearsightedness — especially in East Asia, where prevalence among school-aged children can reach up to 70%.

Can simply spending more time outside in daylight help protect children from developing myopia?

In this episode, our guest Asst. Prof. Raymond P. Najjar (National University of Singapore) breaks down:

• What we know about the link between light exposure and myopia in children

• Why kids aren’t spending enough time outdoors (and no — it’s not just because of tablets!)

• How we might be able to rethink indoor lighting in schools to better support healthy visual development

Links and resources related to the episode’s content

• The influence of lifestyle and the environment on myopia: https://doi.org/10.1186/s40101-024-00354-7

• Outdoor activity reduces the prevalence on myopia in children: 10.1016/j.ophtha.2007.12.019

• Prompting parents to make their kids spend more time outdoor: https://jamanetwork.com/journals/jamapediatrics/fullarticle/2796425

• More info on the LightSPAN project: https://eyenbrain.com/project-lightspan/

Timestamps

(00:00) Intro and questions to kids

(02:37) Guest introduction

(03:30) Understanding myopia: causes and prevalence

(06:58) The role of light and the environment

(11:45) Challenges in increasing outdoor time in kids

(16:27) Improving indoor lighting for myopia control: the LightSPAN project

(23:09) Behavioural interventions with parents

(27:14) Light exposure and myopia control in adults

(29:30) Conclusions

(31:07) Outro with more kids snippets

How does life in cities versus rural areas shape our circadian rhythms? How does access to electricity — or the lack of it — impact sleep timing? And what happens to our circadian rhythms when we move from an urban setting to camping outside?

Our guest Luísa Klaus Pilz (Charité - Universitätsmedizin Berlin) comments on field studies carried out when she was a PhD student and postdoc at the Federal University of Rio Grande do Sul (Laboratório de Cronobiologia e Sono - HCPA/UFRGS).

Links and resources related to the episode’s content

• https://www.nature.com/articles/s41598-018-29494-4

• https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.773969/full

• https://www.cell.com/current-biology/fulltext/S0960-9822(16)31522-6

Timestamps

(00:00) Intro

(00:44) Questions from a Londoner

(03:07) Guest introduction

(03:57) Why care about rural vs urban light?

(07:28) Sleep changes with urbanization

(09:40) The effects of electricity and artificial light

(10:49) Quilombola communities

(16:38) Metabolic health differences

(20:53) Rural occupations and light exposure

(24:00) Other differences in behaviour

(25:22) Adapting to a different environment

(28:27) Future research questions

(31:49) Outro

For feedback and questions, you can contact us at: lightoclock@tuebingen.mpg.de

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On 30 March 2025, Europe will switch to Daylight Saving Time (DST), moving clocks forward by one hour. While many people enjoy longer evenings, scientists in sleep and circadian research argue that DST can be harmful to our health. In this episode, we dive into the controversy surrounding DST and answer three key questions:

• Why do chronobiologists want to get rid of DST?

• What does the evidence say about DST’s impact on road traffic accidents?

• What does the public think about abolishing DST?

We hear from experts, including Prof. Till Roenneberg, Prof. Sara Montagnese and Prof. Andrew Coogan, to break down the scientific and political debates around DST. Plus, we explore the short- and long-term health effects of DST on our health, the challenges of assessing this impact, and why public opinion seems to contradict expert recommendations when it comes to clock changes.

Timestamps

(02:11) DST and time zones
(04:12) What happens to our clock when we change to DST
(05:35) Short- and long-term consequences on DST
(07:51) DST and social jet-lag
(10:10) Challenges of studying DST effects on our heath
(11:05) DST and driving performance
(13:45) DST and road traffic accidents
(17:37) Geography matters
(20:30) What does the public think about clock changes?
(23:15) Results of survey on public opinions in Ireland
(26:20) Wording matters: Summer time/Winter time
(30:24) Is this the battle chronobiologists should fight?
(33:00) Summary and outro

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Website: https://www.tscnlab.org/podcast