How Your Sleep Habits Shift As Daylight Disappears

Your body is naturally tuned to the rhythm of light and dark. Sunlight helps regulate your circadian rhythm, the internal process that tells you when to feel awake and when to sleep. When sunlight hits your eyes, it signals your brain to suppress melatonin, the hormone that makes you sleepy. As daylight disappears during fall and winter, your body receives fewer of these signals, leading to increased melatonin production earlier in the day. This can lead to earlier drowsiness, later wake times, and a general feeling of sluggishness. 

This isn’t a design flaw - it’s evolutionary. For much of human history, our ancestors adapted their sleep schedules to match available sunlight, sleeping longer during darker months when hunting and gathering are less productive. While modern society has much eliminated this need, our biology hasn’t caught up.

Meanwhile, darker mornings delay the suppression of melatonin, so you might find it harder to wake up or feel alert. This seasonal disruption can make your body feel “out of sync,” especially if your schedule doesn’t adjust with the changing life. 

What Changes as Days Get Shorter 

• Earlier bedtimes: Many people naturally shift toward earlier sleep times as days shorten. Your body starts to produce melatonin earlier in the afternoon, triggering sleepiness well before your summer bedtime. 
• Increased sleep duration: It’s not just about going to bed earlier, many people also sleep longer. During winter, it’s not uncommon to sleep 1-2 more hours more than you do in summer months. This extended sleep isn’t necessarily lazy; it’s your body responding to seasonal cues. 
• Mood dips and low energy: Less sunlight also means less serotonin, a neurotransmitter linked to happiness and focus. This can lead to mild mood dips, or for some, symptoms of seasonal affective disorder (SAD).
• Changes in REM sleep: Some research suggests that seasonal variations can affect the composition of your sleep, potentially increasing time spent in deeper sleep stages during winter.

Individual Variation Matters

Not everyone experiences these changes equally. Your response depends on several factors: 

• Latitude: People living further from the equator experience more dramatic seasonal light changes and typically notice more significant sleep shifts than those in regions with more consistent daylight year-round. 
• Genetics: Some people are more sensitive to light changes than others. If you’re naturally a “night owl” or have a longer circadian rhythm, you may experience more pronounced shifts. 
• Personal Sensitivity: Individuals vary in their susceptibility to seasonal affective disorder and related sleep changes. Some people breeze through winter with minimal adjustment, while others struggle significantly. 

What You Can do to Reset Your Rhythm 

The key to navigating shorter days is to work with your body's biology, not against it. Here's how to support a healthy sleep cycle as daylight disappears: 

1. Seek natural light early: Spend 15 - 30 minutes outside within an hour of waking. Morning light helps supress melatonin and boosts alertness for the day. 
2. Dim your evenings: Lower your home lighting and reduce screen exposure 1-2 hours before bed. Warm, amber-toned lights mimic sunset and cue your body for rest.
3. Keep your sleep schedule consistent: Go to bed and wake up at the same times (even on weekends) to stabilize your circadian rhythm.
4. Move during daylight hours. Daytime exercise, especially outdoors, reinforces natural light exposure and improves sleep quality at night. 
5. Create a wind-down ritual: Reading, stretching, or journaling can signal to your nervous system to slow down, replacing that late night scroll with calm. 

It’s perfectly normal for your sleep habits to shift as daylight fades. Your body is simply responding to the environment,  something humans have done for thousands of years. By leaning into these natural changes and supporting your rhythm with light, routine, and rest, you can move through the darker months feeling more energized and in control.