Tired Minds, Stubborn Emotions: How Does Sleep Shape Our Daily Mood?
- Emma Sullivan
- Oct 24
- 4 min read
Research Spotlight Blog No.5
Emma Sullivan is a Postdoctoral Research Associate in the Department of Psychology at the University of York. She completed her BSc in Psychology at York in 2016 and her MSc in Psychological Research at the University of Oxford in 2018. Returning to York, she earned her PhD in Cognitive Neuroscience and Neuroimaging in 2024. Her research focuses on how sleep shapes emotional processes and mental health. In this blog Emma will discuss a pilot project she is currently conducting looking at how sleep shapes daily mood, which was funded by the Network.
Why Sleep Might Help Us Bounce Back from Bad Moods
We all feel sad or anxious from time to time, but for some people, those negative moods can be hard to shake off. Understanding why they stick around, and how we might manage them, is key to supporting mental health. Poor sleep is known to increase the risk of mental health problems, so during my PhD, I wanted to find out whether sleep also affects how long negative moods last.
Tracking Mood and Sleep
To explore this, I created a task where participants watched a series of short video clips and rated their mood after each one. This let us see how their mood changed over time. I also asked participants to report how well they usually sleep. The results showed that people who slept better had moods that shifted more easily, so their negative feelings came and went more quickly. This suggests that getting good-quality sleep might help protect mental health by helping us recover faster from low moods.
But there’s more to sleep than just “how well” someone feels they slept. Certain parts of sleep, like rapid eye movement (REM) sleep and sleep spindles (brief bursts of brain activity), are linked to how we process emotions. These features might also influence how long negative feelings stick around, but no one has studies this directly. I wanted to explore sleep in more detail to see how it connects to mood persistence.
Measuring Sleep and Mood in Daily Life and the Lab
With funding from the Network, I am currently running a small-scale pilot study to investigate this question. We are tracking sleep and mood both in daily life and in a controlled laboratory setting.
Daily life sleep: Participants wear Garmin wristwatches each night. These monitors track their rest while they follow their normal routines.
Lab sleep: We are using a method called polysomnography, which records brain activity while participants asleep. This allows us to study detailed sleep features, like time spent in REM sleep or the number of sleep spindles during the night.
To track mood:
Daily life: We are using the experience sampling method. Participants download a smartphone app and rate different mood states (such as how happy or how sad they are feeling) several times a day.
Lab: Participants complete the film clip task, where they watch a series of emotional and neutral clips and then rate how they feel after each one.
We are using a special modeling technique to see how mood at one moment predicts mood at the next. This gives us a measure of mood persistence, which we can then compare with sleep data to understand how different sleep features might influence the way mood carries over from one moment to the next.
Involving with Young People
An important part of this study involves working closely with a young person advisory group. Their input has helped shape the study design and reduce barriers to participating in overnight sleep research. They refined the questions asked in the experience sampling app, improved watch instructions, and suggested ways to make sleep lab visits less intimidating. For example, participants can now visit the lab ahead of time and receive a leaflet outlining the overnight protocol, covering topics like what polysomnography involves, what to bring, and what to expect from lights out to morning.
Learning from Experts
I was fortunate to attend a three-day training course on experience sampling method at KU Leuven in Belgium. This training helped me design the experience sampling part of the study and connect with researchers at the forefront of this method.
I also attended my first international sleep conference, World Sleep 2025 in Singapore, where I presented my broader PhD work and discussed this study with colleagues. Both experiences were invaluable for refining methods and building research networks.
Looking Ahead
Although this study is small-scale, the findings and participant feedback will help guide larger projects. For example, we could explore how the relationship between sleep and mood persistence differs in people with depression or anxiety. If we find specific sleep features are important, there are also exciting possibilities for intervention.
One such technique is auditory brain stimulation. This involves playing carefully timed sounds while a person sleeps, which can boost brain activity like spindles. By enhancing these sleep patterns, it might be possible to help reduce the persistence of negative moods.
This research is still in its early stages, but it highlights how sleep quality and specific brain activity during sleep could help protect mental health. I would like to once again thank the Network for enabling me to conduct this research and supporting my development as an early-career researcher.
Blog by Emma Sullivan