You’re exhausted all day… then suddenly wide awake at 10:30 pm
Your anxiety seems to spike at night.
You wake up at 3 am with your mind racing.
You feel heavier, slower, or more withdrawn every winter.
Or maybe nothing feels obviously “wrong” … but something just feels off.
It’s easy to assume this is just stress, overthinking, or burnout.
But what if part of this isn’t just psychological, it’s timing?
Your Brain Runs on a 24-Hour Clock
Inside your brain is a biological timing system that runs on roughly a 24-hour cycle. These are called circadian rhythms.
They are largely regulated by light (especially natural light), and they help coordinate many processes in the body, including:
- Sleep and wakefulness
- Hormones like melatonin (sleep) and cortisol (stress)
- Body temperature
- Energy levels
- Emotional regulation
Circadian rhythms don’t just determine when you feel sleepy, they influence how your brain and body function throughout the entire day (Vasey et al., 2021).
When this system is aligned, things tend to feel more stable. When it’s even slightly off, it can affect sleep, mood, and how we handle stress.
When the Clock is Out of Sync (Insomnia)
Sometimes, insomnia isn’t about not being tired, it’s about your brain’s timing system not lining up with your life.
Your body might be ready for sleep, but your internal clock hasn’t started sending “night” signals yet.
This can show up as:
- Feeling wired at night
- Taking a long time to fall asleep
- Waking up in the middle of the night
- Sleeping at inconsistent times
Research shows that our internal clock (often measured by melatonin timing) strongly influences when we feel ready to sleep. When there’s a mismatch between that timing and when we actually try to sleep, people tend to take longer to fall asleep and sleep less overall (Scott et al., 2025).
This mismatch is sometimes called circadian misalignment (Wescott et al., 2022).
And importantly, it is fairly common.
Modern life makes it easy for our schedules to drift away from our biology (Walker et al., 2020; Scheer & Chellappa, 2023).
Why Sleep Problems Can Make Anxiety Feel Worse
If you’ve ever noticed your anxiety feels worse after a bad night of sleep, you’re not imagining it.
Sleep and emotional regulation are deeply connected (Scheer & Chellappa, 2023).
When sleep is disrupted:
- The brain becomes more reactive to stress
- Emotional regulation becomes harder
- The nervous system stays more activated
In fact, research shows that poor sleep doesn’t just leave people tired, it can leave them physiologically and emotionally activated the next morning, with higher levels of restlessness and stress (Rösler et al., 2024).
There’s also a biological piece to this.
Cortisol (one of the body’s main stress hormones) follows a daily rhythm. It typically peaks in the morning and gradually declines throughout the day. This rhythm helps regulate energy, stress, and alertness (O’Byrne et al., 2021).
But when sleep is disrupted, or circadian rhythms are misaligned, this pattern can shift. For example, sleep loss has been shown to keep cortisol elevated later in the day, making it harder to wind down (O’Byrne et al., 2021).
A helpful way to think about it:
Sleep loss doesn’t create anxiety out of nowhere, but it reduces the brain’s ability to regulate it.
Seasonal Depression: When Light and Timing Shift
If you notice your mood changes in the winter, you’re not alone, and it’s not simply about “liking” or “disliking” the season.
Light is the most powerful signal for regulating circadian rhythms.
In the winter:
- Sunrises happen later
- Daylight exposure decreases
- Morning light is reduced
This can shift the body’s internal clock later, meaning your biological “night” may extend further into the morning.
Research suggests that in seasonal depression, this delay in circadian timing can create a mismatch between the body’s internal clock and daily life, which may contribute to low mood and energy (Wescott et al., 2022; Vasey et al., 2021).
This is one reason why morning light exposure (including light therapy) can be helpful. It helps shift the internal clock earlier and restore alignment.
Seasonal depression isn’t just about mood, it’s also about biological timing responding to changes in light.
Why Modern Life Makes This Harder
Circadian rhythms evolved in a world with consistent light and dark cycles.
But modern life often looks very different.
Things like:
- Late-night screen use
- Artificial lighting
- Irregular sleep schedules
- Shift work
- Social jet lag (sleeping differently on weekends vs weekdays)
Can all disrupt circadian timing (Walker et al., 2020; Scheer & Chellappa, 2023).
Even small, repeated shifts in timing can affect:
- Sleep quality
- Emotional regulation
- Stress response systems
- Overall mental health
Over time, this misalignment can increase vulnerability to anxiety and depression (Walker et al., 2020; Vasey et al., 2021)
Small Shifts That Can Support Your Rhythm
This isn’t about “fixing” yourself, it’s about gently supporting your biology.
Some small, research-informed ways to support your circadian rhythm include (Scott et al., 2025; Wescott et al., 2022)
- Waking up at a consistent time (this has one of the strongest impacts)
- Getting natural light in the morning, ideally within 30 minutes of waking up
- Keeping the lighting softer in the evening
- Reducing bright screens late at night
- Creating a wind-down routine before bed
- Keeping sleep and wake times relatively consistent, even on weekends
These are not quick fixes, but small shifts in timing can sometimes create meaningful changes in how you feel over time.
Where Therapy Can Fit In
If sleep, anxiety, or mood changes have been ongoing, it’s not something you have to navigate alone.
Therapy can help explore patterns like:
- Difficulty falling or staying asleep
- Anxiety that worsens at night or in the morning
- Season shifts in mood
- The relationship between stress, sleep, and daily routines
Certain approaches, like anxiety-focused therapy or behavioural strategies, can help support both mental health and sleep patterns.
Just as importantly, therapy can help shift the narrative from “something is wrong with me” to “my body is trying to regulate something, and I can learn to support it”
A Final Thought
Mental Health is shaped by things like life experiences, relationships, environment, and biology.
Circadian rhythms are one part of that picture.
Understanding how your internal clock influences your sleep, energy, or mood can offer a different kind of perspective, one that is less about blame and more about alignment.
Sometimes, it’s not about trying harder. Sometimes it’s about working with your timing, not against it.
References
O’Byrne, N. A., Yuen, F., Butt, W. Z., & Liu, P. Y. (2021). Sleep and circadian regulation of Cortisol: A short review. Current Opinion in Endocrine and Metabolic Research, 18, 178–186. https://doi.org/10.1016/j.coemr.2021.03.011
Rösler, L., van Kesteren, E.-J., Leerssen, J., van der Lande, G., Lakbila-Kamal, O., Foster-Dingley, J. C., Albers, A., & van Someren, E. JW. (2024). Hyperarousal dynamics reveal an overnight increase boosted by insomnia. Journal of Psychiatric Research, 179, 279–285. https://doi.org/10.1016/j.jpsychires.2024.09.032
Scheer, F. A. J. L., & Chellappa, S. L. (2024). Endogenous circadian rhythms in mood and well-being. Sleep Health, 10(1). https://doi.org/10.1016/j.sleh.2023.07.012
Scott, H., Lovato, N., Comas, M., Bartlett, D., Grunstein, R. R., Lack, L., & Gordon, C. J. (2025). Circadian rhythm timing and associations with sleep symptoms in people with insomnia. Journal of Pineal Research, 77(5). https://doi.org/10.1111/jpi.70069
Vasey, C., McBride, J., & Penta, K. (2021). Circadian rhythm dysregulation and restoration: The role of melatonin. Nutrients, 13(10), 3480. https://doi.org/10.3390/nu13103480
Walker, W. H., Walton, J. C., DeVries, A. C., & Nelson, R. J. (2020). Circadian rhythm disruption and mental health. Translational Psychiatry, 10(1). https://doi.org/10.1038/s41398-020-0694-0
Wescott, D. L., Wallace, M. L., Hasler, B. P., Klevens, A. M., Franzen, P. L., Hall, M. H., & Roecklein, K. A. (2022). Sleep and circadian rhythm profiles in seasonal depression. Journal of Psychiatric Research, 156, 114–121. https://doi.org/10.1016/j.jpsychires.2022.10.019
