Episode 72 - How Daylight Saving Time Is Wrecking Your Biology

circadian rhythm daylight saving hormone health menstrual health sleep science

Daylight saving time is a massive biological stressor, & we are not loud enough about that. Every spring, millions of people experience what researchers call a "population-scale circadian disruption event," yet most of us just grab an extra coffee, joke on social media about feeling tired, & move on as though nothing significant happened.

But when you stop looking at this as a cultural inconvenience & start examining it through the lens of physiology, the picture changes completely. The research is undeniable: daylight saving time, especially the spring transition, correlates with measurable spikes in heart attacks, strokes, fatal car accidents, workplace injuries, metabolic dysregulation, & mood instability. And there's a much deeper conversation we're still not having enough about the effects on hormone health, fertility, & the menstrual cycle.

The body does not organize itself around the wall clock. Your body organizes itself around light & darkness. Daylight saving time asks millions of people to suddenly live against that reality overnight. In this episode, I'm walking through the history of daylight saving time, why it's fundamentally unnatural from a biological perspective, what circadian disruption does to melatonin, cortisol, insulin sensitivity, cardiovascular health, & why this conversation absolutely belongs in hormone health & menstrual cycle awareness.

Topics covered

In this episode, we discussed

Reflecting on an intensely difficult year & choosing to see lessons in hardship
Health journey through typhoid fever, pregnancy loss & thyroid dysfunction
Deciding to go all in on healing rather than splitting focus with business
Learning horseback archery to honor dad's love of archery & overcome riding trauma
Picking up crochet to honor grandmother & connect with ancestors through embodied skills
Cultivating intuition by choosing embodied practices over logical thinking
Finding peace through skills that require full presence & attention
Discovering audiobooks paired with crochet as perfect combination
How ancestral skills bring deceased loved ones closer in felt presence
Choosing to be your own peace & peace for those you love

Listen to the Episode

Timestamps

[02:40] Daylight saving time as massive biological stressor we're not critical enough about

[05:58] DST created for World War I economics, not health: half a percent energy savings

[10:25] Circadian system is light-based, not watch-based: social time vs solar reality

[15:11] 24% increase in heart attacks on Monday following spring DST shift

[18:13] Even one or two nights of poor sleep measurably impairs insulin sensitivity

[22:13] Melatonin disruption: biology told it's still daytime when it should sleep

[24:59] Increased fatal car accidents & workplace injuries: population-scale safety impact

[27:14] Personal ADHD experience: DST destroys the "ocean of time" morning rhythm

[29:28] Menstrual cycle is energy-dependent, timing-dependent & circadian-regulated

[33:17] Standard time better than permanent DST: morning light is strongest circadian anchor

This Was Never About Biology—It's About Economics

Let me be clear: daylight saving time was never created for health. It was introduced during World War I as an economic & industrial strategy to maximize daylight hours during the workday. Research shows maybe half a percent of energy saving. Half a percent.

Why would you throw all of your biology under the bus to save 0.5% of energy output?

From the beginning, it was about squeezing more usable labor & activity out of the day. One of the core problems of modern life is that we keep taking systems designed for economics & industry & then acting shocked when the body struggles inside of them.

Biology does not care what politicians, governments, or social policy decide the clock should say. Your cells still respond to light & darkness. When the environment is thrown off, it throws off your biology.

How Circadian Disruption Actually Works

Your circadian rhythm is your internal 24-hour timing system, regulated by light entering your eyes. It controls sleep, hormones, appetite, body temperature, mood, metabolism, & reproductive signaling.

At the center is your suprachiasmatic nucleus (SCN)—the mother clock in your brain. Morning light tells your brain: the day has begun. Melatonin production is suppressed, cortisol rises (the cortisol awakening response), & your physiology gets ready for the day. In the evening, as light falls, melatonin production begins, preparing you for sleep.

The Spring Shift Problem

When clocks move forward in spring, mornings become darker & evenings become lighter. The problem isn't losing an hour—it's that the timing of light exposure changes in the most disruptive way possible:

Less light when you need it most (morning)
More light when it's disruptive (evening)
Delayed melatonin release
Pushed-back sleep onset
Forced-earlier wake time (but sunrise happens way after)
Misaligned cortisol timing
Body asked to function before it's truly ready

This creates what we call social jetlag—a government-mandated circadian disruption event people are expected to absorb as though nothing happened.

The Cardiovascular Crisis: 24% Increase in Heart Attacks

Here's what people need to understand: studies found a 24% increase in heart attacks on the Monday immediately following the spring daylight saving time shift.

Studies from Sweden, Finland, Germany, Croatia, Brazil, & Mexico found similar patterns. When the pattern keeps showing up across populations, it's real.

The cardiovascular system is highly sensitive to sleep loss, autonomic stress, inflammatory signaling, blood pressure changes, & circadian disruption. It doesn't take a giant insult to create measurable risk.

Research also found an 8% increase in stroke risk during the first two days after the spring shift. This hits people with less physiological resilience hardest: immunocompromised individuals, people with cancer, older adults.

We also see increased fatal car accidents & workplace injuries because sleep deprivation impairs reaction time, vigilance, decision-making, & motor coordination. When that's happening across an entire population at the same time, roads & workplaces become less safe.

Metabolic Circadian Disruption: Insulin, Appetite & Blood Sugar

Even one or two nights of poor sleep can measurably impair insulin sensitivity. Your cells become less responsive to insulin, glucose regulation becomes less efficient, blood sugar becomes less stable.

The spring shift creates several days of degraded sleep quality, fragmentation, delayed sleep onset, & persistent circadian strain. Layer this together: less sleep + lighter evenings + darker mornings + delayed melatonin + altered cortisol = metabolic dysregulation.

During this transition, people experience (& I'm going through this right now—my cravings are through the roof):

More hunger & worse cravings
More sugar or carb seeking
Lower energy & poor workout recovery
Worse blood sugar stability
More irritability & stress reactivity

This circadian disruption matters even more for people with insulin resistance, PCOS, pre-diabetes, or those in their luteal phase (when you're naturally more insulin resistant).

The Hormone Cascade

When sleep is shortened or fragmented:

Leptin goes down (less satiety)
Ghrelin goes up (more hunger)
Cortisol timing gets misaligned

Now you have stress hormones off, appetite hormones off, blood sugar regulation off, & a body trying to function on worse sleep. Most people reach for more caffeine, push through, maybe drink alcohol to unwind, stay inside all day—which makes the circadian disruption worse.

Melatonin, Cortisol & Mood: The Circadian Disruption Trifecta

When daylight saving time gives us more light later in the evening, melatonin release gets suppressed or delayed. People don't just go to bed later by choice—their biology is being told: it's still daytime.

Melatonin isn't just a sleep hormone. It's involved in repair, antioxidant protection, mitochondrial health, immune signaling, & reproductive physiology.

Morning cortisol is supposed to rise with morning light. But during the spring shift, mornings are darker & wake time is earlier. Now you have a blunted or poorly aligned cortisol rhythm:

Difficulty waking & grogginess
Feeling tired but wired
Poor energy & sluggish mood
Second-wind energy at 9 or 11 p.m. when you don't want it (which interrupts sleep)

Serotonin is also disrupted because daylight exposure plays an important role in mood. When people get less morning light & more evening light, this contributes to mood disruption & poor sleep regulation. Research links daylight saving time shifts to worsened mood, anxiety, depressive disorders, & emotional instability.

My ADHD Experience

Personally, I have ADHD, & this circadian disruption messes with me so much. I had such a good rhythm. The sun was rising around 6 a.m., & I felt like I had an ocean of time before starting work at 9. I could journal, walk, go to the gym, have breakfast.

Now the sun rises at 7, & there's less time between sunrise & 9 a.m. It gives me so much anxiety. I feel pressured & stressed. I do really well when I have a rhythm timed around light availability during the day. Now it just feels all messed up. I actually hate how it feels in my body.

Circadian Disruption, Menstrual Cycles & Fertility

This doesn't get talked about nearly enough. Circadian rhythm disruption doesn't just stay in the sleep or metabolic lane—it moves downstream into reproductive physiology.

The menstrual cycle is energy-dependent & timing-dependent. Every phase requires precision from both reproductive hormones & circadian hormones:

Follicular phase needs energy & signaling for follicle growth & rising estrogen
Ovulation is a highly coordinated signaling event
Luteal phase depends on progesterone production (deeply energy-dependent & mitochondria-dependent)

Your menstrual cycle is not just hormonal. It's also circadian, mitochondrial, metabolic, light-informed, & stress-sensitive.

When circadian rhythm is disrupted, the body may respond with:

Irregular cycles
Delayed or disrupted ovulation
Lower progesterone resilience
Worse PMS
More inflammation & blood sugar instability
More stress signaling

Insulin affects ovarian function, androgen balance, & follicle development. When sleep disruption impairs insulin sensitivity through circadian misalignment, it impacts menstrual cycle health & fertility—especially for people with PCOS, irregular cycles, luteal phase issues, or chronic stress.

Daylight saving time belongs in the hormone health conversation because the body reads light as information, & when timing information is distorted, reproduction is one of the systems that becomes less stable.

Standard Time vs. Permanent Daylight Saving Time

Even if we agree to stop switching clocks, permanent daylight saving time isn't necessarily the solution.

Circadian researchers argue that standard time is better for health because it preserves more morning light—& morning light is the strongest anchor for the circadian system.

More evening light may feel socially convenient, nicer for shopping or outdoor activities, but it doesn't mean it's better for the biology of sleep, metabolism, mood, or hormone regulation.

What feels fun economically or culturally is not always what best supports human physiology. We have a lot of health issues in society that could be positively impacted if we included circadian misalignment in our health assessments.

The Bottom Line

Daylight saving time is a biological stressor, & we are not loud enough about that. This policy was never built around human biology—it was designed for economic benefit, for productivity, for squeezing more output from human bodies.

I don't want to create fear, but I do want to create critical conversation. We accept so many things that prioritize economic benefit over biological coherence. We need to start asking questions when policies start affecting our biology—because our biology is everything.

The circadian disruption from daylight saving time isn't just about feeling tired for a few days. It's about heart attacks, strokes, metabolic dysfunction, mood instability, & reproductive health impacts that ripple through entire populations twice a year. Your body organizes itself around light & darkness, not social policy. Every spring, we're asked to pretend otherwise. Every spring, the research shows us the cost.

Key Takeaways

Daylight saving time is a population-scale circadian disruption event with measurable health impacts, not just inconvenience
24% increase in heart attacks on Monday following spring shift plus increased strokes, fatal accidents, & workplace injuries
Even one night of poor sleep impairs insulin sensitivity leading to worse cravings, blood sugar instability, & metabolic dysfunction
Spring shift creates darker mornings & lighter evenings disrupting melatonin, cortisol, & serotonin in the most harmful pattern
Circadian disruption affects menstrual cycles & fertility because reproductive physiology is timing-dependent & light-informed
The policy was created for World War I economics to squeeze more labor & productivity, not for human health
Standard time is better than permanent daylight saving time because morning light is the strongest circadian anchor
People with ADHD, metabolic issues, & hormone imbalances may experience circadian disruption more intensely

Transcript

[00:00:00] Iris Josephina: You are listening to the podcast of Iris Josephina. If you are passionate about exploring the menstrual cycle, cyclical living, body wisdom, personal growth, spirituality, and running a business in alignment with your natural cycles, you're in the right place. I'm Iris. I'm an entrepreneur, functional hormone specialist, trainer and coach, and I am on a mission to share insights, fun facts, and inspiration I discover along the way as I run my business and walk my own path on earth. Here you'll hear my personal stories, guest interviews, and vulnerable shares from clients and students. Most people know me from Instagram where you can find me under @cycleseeds, or they have been a coaching client or student in one of my courses. I'm so grateful you're here. Let's dive into today's episode.

[00:00:56] Iris Josephina: Hey, and welcome to a new episode of the Inner Rhythms Podcast. It took me a minute to come back online and spend some time on my podcast. My personal private life has been extremely hectic, and I simply didn't have the capacity in any way, shape or form to create a lot of content. The good news is that in the midst of all this craziness, I got a kitten and he is sitting here next to me. You may hear him purr. His name is Bibo and he is the sweetest little one. I'm just so happy he is in my life. Taking care of a little animal just brings me so much fulfillment.

[00:01:41] Iris Josephina: For today's episode, I want to discuss a topic that actually made me really angry. Maybe you have noticed, especially if you are in Europe or in every other country that practices daylight saving time, oh my God, it's such a mess. This whole practice, I have so much to say about it. So grab a cup of tea, sit down or go on a walk or do your workout and listen to everything that I have to say. And I'm going to start off by saying daylight saving time is a massive biological stressor, and we are not loud enough about that. We are not critical enough about that, and I am going to take a deep dive with you into circadian rhythm, hormones, metabolism, mood, and the menstrual cycle. So let's get started.

[00:03:07] Iris Josephina: So every year the conversation around this time is the same. People complain about being tired for a few days around daylight saving time. They joke about it on social media, at least that's what I've seen this year. People grab an extra coffee, maybe they feel a little off or a little foggy or a little bit more irritable than usual, and most people just move on and don't really care about it. But what usually does not get talked about enough is what is actually happening inside the body during that transition window.

[00:03:39] Iris Josephina: Because when you stop looking at this as a cultural inconvenience and really start looking at it through the lens of physiology, the picture changes completely. And once you understand the science, you're like, what the actual F are we doing to our bodies? And when you look at the actual research, daylight saving time, especially the spring transition that we're going through right now, is not just annoying. It really is a population-scale circadian disruption event, and the downstream health effects show up very clearly in research and numbers. And it is honestly beyond me that nobody is doing something about this. We see more heart attacks, more strokes, more fatal car accidents, more workplace injuries, sleep disruption, metabolic dysregulation, mood instability, and in my view, a much deeper conversation we're still not having enough is about the effects on hormone health, fertility, and the menstrual cycle.

[00:05:11] Iris Josephina: Because the thing is, and you know, if you've done any of my courses, especially my course Cyclical, you know that the body does not organize itself around the wall clock. Your body organizes itself around light and darkness, and daylight saving time asks millions of people to suddenly live against that reality, that fact, that blueprint, overnight. So today I want to walk through the history of daylight saving time, why it is fundamentally unnatural from a biological perspective, what it does to circadian rhythm, what it does to melatonin, cortisol, serotonin, insulin sensitivity, cardiovascular health, and metabolic health, and why this absolutely belongs in the conversation around the menstrual cycle and fertility health too.

[00:05:58] Iris Josephina: So the first thing that I want to say is that daylight saving time was never, ever, ever created for health. It was introduced during World War I as an economic and industrial strategy. Basically, it was seen as a way to conserve energy and maximize daylight hours during the workday. From this energy perspective, there has been some research that actually shows just about half a percent of energy saving, which I think is crazy. Like why would you throw all of your biology out to save half a percentage of energy output? So from the beginning it was about so-called efficiency. It was about output, it was about productivity, and technically it was about squeezing more usable labor and activity out of the day. And it was not created because anybody thought it was good for the nervous system. It was not because anybody thought it supported hormone health and it was not created because it made human biology more coherent, which is in essence what we want when we look at health. We are looking for biological coherence, and this is not it. Oh my God, this stuff makes me so angry. I'm just going to try to contain my anger as I move through this episode because there is just too much.

[00:07:19] Iris Josephina: So I think one of the core problems of modern life is that we keep taking systems designed for economics and industry and then acting shocked when the body struggles inside of them. Daylight saving time is one of the clearest examples of that. It's a social policy imposed onto biology with the desire to create more output, more consumerism, more labor out of people. There has also been some research that when we do daylight saving time, people go shopping more and go out of the door later to buy things. And with all of this, I'm just starting to wonder, are we really so brainwashed that we just blindly disrupt our biology for the sake of culture and social policy? Because the thing is, biology does not care what politicians, governments, office culture, or social policy decides that the clock should say. Your cells simply still respond to light and darkness. The environment does change and the environment is thrown off, so it throws off your biology.

[00:08:54] Iris Josephina: Let me explain to you why daylight saving time is biologically unnatural, and this is just my standpoint. Daylight saving time is unnatural. Not in some dramatic, vague way, no. It's literally disruptive, physiologically wrong, because if you boil it down to just plain biology, humans are biologically primed for brighter days, darker nights, morning light exposure, and evening darkness to set all the body clocks, specifically our suprachiasmatic nucleus, which is our mother clock in our brain, and all of the daughter clocks, which are the peripheral clocks in every single hormone and every single organ. And this contrast of light and darkness tells the brain what time it is, and it anchors our circadian rhythm. We are really designed to live in relationship with the rising and setting of the sun. And we are not primed or designed to live with a social clock that suddenly jumps forward by an hour and expects the entire endocrine, nervous, metabolic, and cardiovascular system to just adapt instantly. That is not how the body works. Your circadian system is a light-based timing system. It's not a watch-based timing system. And when social time suddenly shifts but our solar reality does not, your body and your biology experience that as a mismatch, and that mismatch is what we call circadian misalignment.

[00:10:50] Iris Josephina: Let me go over what the circadian rhythm is, very briefly. If you want to learn more about this, get on the waitlist for my course Cyclical, because I go very, very deep into everything that I'm talking about today and how you can support your body. So the circadian rhythm is basically your internal 24-hour timing system. It regulates sleep and wake timing, hormone production, appetite and digestion, body temperature, your alertness and focus, your immune function, your mood, your metabolism, and your reproductive signaling. At the center of the system is your SCN, what I like to call the mother clock, your suprachiasmatic nucleus, and this mother clock is primarily synchronized by light coming into your eyes. Morning light basically tells your brain, hello, the day has begun. And as light enters the eye, melatonin production is suppressed and cortisol begins to rise in a healthy morning rhythm. This is also known as the cortisol awakening response, and that morning cortisol rise is not inherently bad. People these days tend to see, oh my God, cortisol's bad, stress. No. Cortisol is literally what wakes you up in the morning, mobilizes energy in your body, sharpens your alertness, and it really gets your physiology ready for the day. And then later in the evening, as light levels start to fall, your pineal gland begins producing melatonin, which helps prepare the body for sleep and nighttime repair.

[00:12:27] Iris Josephina: So I hope you're already seeing the problem. If we reduce morning light and increase evening light, we distort the signals that tell the body when to wake and when to sleep. And that is exactly what daylight saving time does. It messes up the system. The spring shift is the real problem. So the one that we've just moved through, if you are in a country where we have adopted daylight saving time. When clocks move forward in spring, mornings literally become darker and evenings literally become lighter. And it sounds like this is some small thing, but physiologically, oh my goodness, it's not small at all. Because the problem is not just that you quote-unquote lose an hour. The real problem is that the timing of light exposure changes in the most disruptive way possible. You get less light when you need it the most, in the morning, and more light when it is disruptive, in the evening. This means melatonin release gets delayed, sleep onset gets pushed to a later time, wake time is forced earlier by a social clock, the sunrise maybe happens way after, and cortisol timing becomes misaligned, and the body is effectively asked to function before it's truly ready. Because we are light beings, and I don't mean this in a woo or spiritual way. We are literally responding to light. This is why the spring shift is consistently associated with more harm than the autumn shift, because the autumn shift moves us onto standard time. It is more connected to our biological time, and the spring shift creates what we can call social jet lag. And unlike an actual jet lag where you get on a plane and you change time zones, this is a government-mandated circadian disruption event that people are expected to absorb as though nothing happened. And to me, that is really crazy. I find it so crazy.

[00:14:39] Iris Josephina: I really want to discuss some research on this because people just brush it off like, oh, for a couple of days I'll feel a little bit bad. But the research is striking. So some of the strongest evidence around daylight saving time concerns the cardiovascular system. There is one study in particular that found a 24% increase in heart attacks on the Monday immediately following the spring daylight saving time shift. A 24% spike on that Monday. Other studies have included data from Sweden, Finland, Germany, Croatia, Brazil, and Mexico, and they have found similar patterns. Researchers still see a modest but statistically significant increase in heart attacks after the spring transition. So even if different countries show slightly different effect sizes, the pattern is real enough that it keeps showing up across populations. And this is where people usually say, but ah, it's just one hour. This is exactly the point. The cardiovascular system is highly sensitive to sleep loss, autonomic stress, inflammatory signaling, blood pressure changes, and circadian disruption, and it does not take a giant insult to create a measurable risk, especially in a vulnerable population.

[00:16:30] Iris Josephina: So what happens when we create acute sleep deprivation and shifts in our body like that? It can elevate sympathetic nervous system activity, it can increase inflammatory signaling, it can disrupt cortisol timing, it can raise blood pressure variability, and just technically put more strain on the cardiovascular system. So when a whole population is suddenly asked to be so misaligned, it should not be surprising that we see an uptick in cardiac events. It's biology. It's what happens. The same story appears with stroke. Research has found an increased stroke risk in the first days following the daylight saving time transition, with one study showing around an 8% increase in stroke risk during the first two days after the spring shift. And this hits people who have less physiological resilience the hardest. So people who are already immunocompromised, people with cancer, older adults. For some people this is a real physiological destabilization event, and I think we need to be much more cautious about this.

[00:17:49] Iris Josephina: Now let's talk about metabolism. This is also a topic that I believe doesn't get enough attention. So one of the most important things that people do not understand is how quickly compromised sleep can disrupt insulin sensitivity. Even one or two nights of restricted or poor sleep can measurably impair insulin sensitivity. That means that your cells become less responsive to insulin, glucose regulation becomes less efficient, blood sugar becomes less stable, and the body needs to work harder to maintain this balance. And that is not some extremely rare scenario. That's just what sleep disruption does. And daylight saving time does not only steal one hour on one night. The spring shift often creates several days of degraded sleep quality, sleep fragmentation, late sleep onset, and just persistent circadian strain.

[00:18:36] Iris Josephina: If we layer all of this on top of one another, what happens? Less sleep, lighter evenings, darker mornings, delayed melatonin, altered cortisol timing, more fatigue, more cravings, worse recovery. People are operating in a more metabolically dysregulated state. This is why during this transition window, people may often experience, and I'm going through that right now, my cravings are through the roof. I have not had cravings in months. People experience more hunger, worse cravings, more sugar or carb seeking, lower energy, poor workout recovery, worse blood sugar stability, more irritability, that's me also because I'm angry about all of this, and more stress reactivity. And this matters even more in people who already struggle with metabolic health. So people who have insulin resistance, or if you are in your luteal phase when this happens, when you're naturally more insulin resistant, it will hit you harder. People who are pre-diabetic, people with PCOS, and people with obesity. And if we keep looking at this metabolic story, sleep does not just affect insulin. It also affects the hormonal systems that regulate hunger, the feeling of satisfaction after a meal, and stress. So when your sleep is shortened or fragmented, leptin tends to go down and ghrelin tends to go up, which means that people often feel hungrier, less satisfied, more impulsive around food, and less metabolically stable overall. At the same time, cortisol is getting pushed around. Normally cortisol should rise in the morning in sync with light exposure and the wake process, but when people are forced to wake earlier while mornings are still darker, that normal cortisol awakening response can become less aligned with actual behavior and clock time. So now you have a stress hormone rhythm that feels off, an appetite hormone rhythm that feels off, blood sugar regulation that feels off, and a body that is trying to function on less and worse sleep.

[00:21:03] Iris Josephina: So what do most people do? I actually had a conversation with a client about this as well. People reach for more caffeine, they push through, they maybe drink alcohol in the evening to unwind. We see in general society that people stay inside all day and don't go outside enough, which makes the cycle worse. And daylight saving time can set off this whole cascade. We have circadian disruption, we have poor sleep, we have impaired insulin sensitivity, we have worse appetite regulation, more fatigue, and stimulants that people ingest, and then even worse sleep. That's why I do not think this should be minimized at all.

[00:21:46] Iris Josephina: If we then dive a little bit deeper into more hormone timing pieces, we can look at melatonin, serotonin, and cortisol again. When we look at melatonin, melatonin is released in response to darkness. It helps you to initiate your sleep, but it's not just a sleep hormone. It's really involved in repair, antioxidant protection, mitochondrial health, immune signaling, and reproductive physiology. So when daylight saving time gives us more light later in the evening, melatonin release gets suppressed or delayed. People do not just go to bed later because they chose to. Their biology is being told it is still daytime, no time to sleep yet. That means that sleep onset can be harder, there is later sleep timing, there is poorer recovery, and there is more circadian drift.

[00:22:33] Iris Josephina: If we then look at cortisol, cortisol is supposed to rise in the morning. Morning light is one of the strongest anchors for that rhythm, but during the spring shift, mornings are darker and wake time is earlier. So now you may have a blunted or poorly aligned cortisol rhythm, which can look like difficulty waking, grogginess, feeling tired but wired, having poor energy, having a sluggish mood. This was me yesterday and today. And then the second wind energy later in the day when you really don't want it, like at nine or eleven PM your body is like, we have a lot of energy, let's go, let's stay up. But obviously this interferes with your sleep.

[00:23:27] Iris Josephina: The last hormone that I want to discuss here is serotonin. Serotonin is also part of this conversation because daylight exposure plays a very important role in mood and daytime neurochemistry. And serotonin is actually a precursor to melatonin, which is your sleep hormone. So when people get less morning light and more evening light, this can contribute to both mood disruption and poor sleep regulation. This is why research has linked daylight saving time shifts, especially the spring one, to worsened mood outcomes, anxiety, depressive disorders, and emotional instability. So from a hormonal and neurochemical perspective, daylight saving time is not neutral at all. It's not just a small thing. It perturbs the timing of melatonin, cortisol, serotonin-related mood regulation, glucose handling, and insulin sensitivity. And that's a lot of physiological disruption for something people still joke about like it's just a cute seasonal annoyance. It's really not that innocent.

[00:24:38] Iris Josephina: And then something that I found interesting. I wasn't really looking at this, but I was doing my research and I found out that the effects of daylight saving time don't stay internally in the body. They also show up externally. Apparently we see an increased fatal car accident rate in the period following the spring shift. And we also see apparently increased workplace injuries. In essence, it makes sense because sleep deprivation impairs our reaction time, it impairs vigilance, it impairs decision making, it impairs motor coordination and attention. So when that is happening across an entire population at the same time, basically what this says is that roads and workplaces become less safe. And this is why some people keep calling this a population-scale circadian disruption event, because apparently it doesn't just affect personal comfort and biology, but apparently it also affects collective safety. That's a big thing.

[00:25:54] Iris Josephina: And we already spoke about serotonin. It shows that circadian misalignment also affects emotional regulation in quite a few ways. So in the days following the spring shift, studies have reported increased depressive symptoms, more mood disturbance, greater irritability, worsened anxiety. And in some cases there is concern around increased suicide risk, although that piece is more complex and should be handled carefully. There is some research that is touching upon that. What I take out of this is that the sleep deprivation and circadian disruption makes people less emotionally resilient. And this fits what we know from broader sleep science. So when your cortisol timing is off, your sleep is fragmented, your serotonin-melatonin rhythm is disrupted, and if you already are under modern life stress, your ability to regulate your mood and your emotions becomes less stable. So if someone already struggles with anxiety, depression, burnout, trauma, or nervous system dysregulation, this transition to daylight saving time can be a real trigger point because physiology is under more stress.

[00:27:14] Iris Josephina: And personally, I have ADHD. It messes with me so much because I had such a good rhythm and I love getting up early. I love getting up with the sunrise and having this feeling that I have an ocean of time. So the sunrise rises here around 6:00 AM and I feel like, wow, I have such an ocean of time before I need to start work at nine. I can do all these things, I can do my journaling, I can go on a walk, I can go to the gym, have my breakfast. But now all of a sudden it's an hour later and the sun rises at seven and there is less time between the sunrise and 9:00 AM when I need to start the things that I need to do during the day. So it gives me so much anxiety that I feel pressured and stressed because there is less time between sunrise and what I need to do during the day. And I think it's really messed up. And I would love to know from other people who have ADHD or even autism, how is this affecting you? Because it's definitely affecting me. I don't like it at all. I actually hate it. I hate how it feels in my body. I don't like feeling pressured. I do really, really, really well when I have a rhythm that is timed around light availability during the day. So I live from sunrise to sunset on standard time when it's more biologically appropriate. And now it just feels all messed up.

[00:29:00] Iris Josephina: And I would love to take this conversation into fertility and menstrual cycle health, because I don't think this gets talked about nearly enough. Circadian rhythm disruption does not just stay in the sleep lane or metabolic health. It also moves downstream into reproductive physiology because the menstrual cycle is a very energy-dependent, timing-dependent rhythm. And every phase of our menstrual cycle requires precision, not only from our reproductive hormones but also from our circadian hormones. The follicular phase requires energy and signaling for follicle growth and rising estrogen. Ovulation is a highly coordinated signaling event. The luteal phase depends on progesterone production, which is deeply energy-dependent and one of the most mitochondria-dependent processes in female physiology. But your menstrual cycle is not just hormonal. It's also circadian, it's mitochondrial, it's metabolic, it's light-informed, it's stress sensitive. So when our circadian rhythm is disrupted, the body may respond with irregular cycles, late or disrupted ovulation, lower progesterone resilience, worsened PMS, poorer energy availability, more inflammation, more blood sugar instability, and more stress signaling.

[00:30:44] Iris Josephina: And we also have the insulin piece. So insulin is not just about blood sugar, it also affects ovarian function, androgen balance, and follicle development. And so when sleep disruption impairs insulin sensitivity, that can absolutely impact menstrual cycle health and fertility too. And it's especially relevant for people who have PCOS or irregular cycles, subclinical infertility, luteal phase issues, PMS, chronic stress, or just fragile metabolic health. So in my opinion, daylight saving time really belongs in the hormone health conversation as well, because the body reads light as information and when timing information is distorted, reproduction is one of the systems that becomes less stable in the body.

[00:31:35] Iris Josephina: And how I see all of this is that people are being asked to live their lives against a clock. The way that modern society has been built up already states this. We are under artificial light for way too many hours. We sit too much. We don't see the sunrise and the sunset. And what I see is that the wall clock says something, but our body clock goes like, yeah, but I want to do this at another time. And it's a chronic timing mismatch. And we already know from shift work what happens when people live in chronic out-of-sync states with their biology. Shift workers have higher rates of obesity, diabetes, coronary heart disease, cancer, mood disorders, reproductive issues, and on average an earlier death. And I'm not saying that daylight saving time is identical to shift work, but I'm saying that it activates the same basic mechanism, which is circadian misalignment. And once you understand that part, it becomes very hard to just dismiss it as something harmless.

[00:32:25] Iris Josephina: And another important point here is that even if people agree that we should stop switching the clocks, it does not automatically mean that permanent daylight saving time is the best solution. A lot of circadian researchers argue that standard time is actually better for health because it preserves more morning light. And morning light is the strongest anchor for the circadian system. More evening light may feel more socially convenient. It may feel nicer for shopping or dinners or outdoor activities, but it does not mean it's better for the biology of sleep, metabolism, mood, or hormone regulation. And what feels fun economically or culturally is not always what best supports human physiology. And I think we should pay a lot more attention to that, because we have a lot of health issues going on in our society these days that I feel could be positively impacted if we included circadian misalignment in our assessment of health issues.

[00:33:52] Iris Josephina: So my recommendation is to take this more seriously than our culture tells us to. Daylight saving time is a policy decision that was never ever built around human biology, and I want us to become more aware of that. It's a biological stressor. I don't want to create fear around this, but I would love to create a critical conversation about this, because we accept so many things in our society that are of economic benefit or productivity-focused. And these things are not in essence bad, but I do feel we need to start asking questions when it starts affecting our biology, because our biology is everything. And if we have biology that responds to proper timing cues, we support our overall general health and we preserve our health on the long term. And I hope that this was both disturbing and inspiring to you. I hope you learned something new today.

[00:35:32] Iris Josephina: If you are interested in learning more about circadian biology and you are seeing that we are inherently cyclical by design, I would love to invite you to join the waitlist for my course Cyclical. I run this course multiple times per year, and inside of it I teach you how to live in accordance with your biological timing and how, when you start doing that, we create a downstream effect and our hormones start to respond and balance on their own. So if you're interested, go check the show notes, sign up for the waitlist, and I cannot wait to see you there. Thank you for listening.

[00:36:03] Iris Josephina: Okay, this wraps up today's episode. Thank you so much for listening. Want to know more about me? The best way to reach me is via @cycleseeds on Instagram, and if you heard something today and you think, oh my God, wow, I learned something new, feel free to share the podcast on your social media and tag me or leave a review or rating. In this way, you help me reach more people like you. Thank you so much.

About the Host

I’m Iris Josephina, a functional hormone specialist, orthomolecular hormone coach, circadian biology practitioner, and entrepreneur. Through Cycle Seeds and The Inner Rhythms Podcast, I support people in reconnecting with their cyclical nature, deepening body literacy, and reclaiming hormonal harmony from a place of sovereignty and embodied knowledge. Most people know me from Instagram, where I share stories, tools, and inspiration on cyclical living, menstrual cycles, fertility, hormones, and more.

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