Seasonal Affective Disorder (SAD) is a type of mood disorder that follows a seasonal pattern, often starting in late fall and continuing through the winter months. It can lead to low mood, depressive symptoms, and changes in everyday life, such as trouble sleeping, weight gain, and social withdrawal. This condition, also known as seasonal depression or winter depression, is linked to reduced daylight hours and less sunlight, which disrupts the body’s internal clock and circadian rhythms.

Melatonin is a hormone produced by the brain called the pineal gland. Increased melatonin production during darker months can contribute to SAD symptoms. This article explores how melatonin and seasonal affective disorder are connected and how melatonin may support better sleep and mood in those experiencing SAD.

Seasonal Affective Disorder (SAD) is a mood disorder that occurs at the same time each year, most often in the late fall and winter months. People with SAD may experience depressive symptoms such as low mood, lack of energy, difficulty sleeping, increased appetite, and social withdrawal.

This condition, sometimes called seasonal depression or winter blues, can interfere with everyday life and make daily tasks feel overwhelming. SAD is believed to be triggered by seasonal changes that reduce daylight hours, which may affect brain chemicals linked to mood and sleep.

While SAD shares similar symptoms with major depressive disorder, it follows a seasonal pattern and usually improves as the seasons change. Major depression can happen any time of year and may not be tied to seasonal light changes. Some people also experience a milder form of SAD or feel symptoms during early spring or early summer, though winter SAD is more common.

Melatonin helps control circadian rhythms or the body’s natural sleep-wake cycles. When sunlight decreases during the winter months, the body may produce more melatonin, which can make people feel sleepy or disrupt their normal sleeping patterns.

This increased melatonin production, especially in people sensitive to seasonal changes, may play a role in the development of SAD. Understanding the link between melatonin and seasonal affective disorder can help identify better treatment options and support overall mental health.

During the darker winter days, reduced exposure to bright light can cause the body to produce melatonin for longer periods, affecting sleep and energy levels. This change happens because the body reacts to light through the eyes, sending signals to the brain to adjust hormone levels.

As daylight hours shorten, people may feel sleepy earlier, experience trouble sleeping, or feel tired during the day. These shifts in melatonin levels and sleep patterns are common contributing factors to SAD symptoms like low energy and mood changes.

The circadian rhythm is the body’s internal clock that tells us when to sleep, wake, and eat. It helps keep sleep patterns and mood in balance. Seasonal changes, especially the lack of sunlight during winter months, can throw off this rhythm.

When the circadian rhythm is disrupted, it can lead to difficulty sleeping, mood swings, and a lower energy level—common signs of SAD. A  misaligned internal clock  may also affect serotonin activity, another factor in seasonal affective disorder SAD and other mood disorders like major depression or bipolar disorder.

Melatonin supplements may support people experiencing seasonal affective disorder by improving sleep and helping the body adjust to seasonal changes. Research suggests melatonin may help regulate the body clock, which could support mood and sleep in people experiencing SAD symptoms.

Studies have shown that people with seasonal affective disorder may have disrupted melatonin production during the darker months. This can lead to increased fatigue and low mood.

Melatonin supplements may help reset the circadian rhythm and support healthier sleep patterns. This could indirectly support energy levels and mood in those with SAD during seasonal changes.

Melatonin may support better sleep quality, positively impacting overall mood in people experiencing SAD. Better sleep can make it easier to manage daily tasks and maintain emotional balance. Melatonin is generally well tolerated and may be a helpful option for those looking for natural treatment options for mood disorders like SAD.

Timing matters when using melatonin to manage SAD. For people with winter depression, taking melatonin in the late afternoon or early evening may help shift the body clock earlier, making it easier to wake up and stay alert during darker winter days.

Taking it too late at night could interfere with sleep or increase daytime drowsiness. Talk to a healthcare provider to find the best schedule for your specific season and symptoms.

Melatonin is available over the counter in different strengths, and finding the correct dose for seasonal affective disorder depends on individual needs and timing.

Most adults with SAD start with a low dose of melatonin, usually between 0.3 mg and 3 mg per day. A lower dose taken in the early evening may be more effective for adjusting the internal clock without making you feel overly sleepy during the day. People with a family history of mood disorders or bipolar disorder should consult their doctor before starting melatonin, as it may not be suitable in all cases.

It’s best to start melatonin at the beginning of the seasonal pattern, usually in late fall. Talk to a healthcare provider to avoid interactions with antidepressant medication or selective serotonin reuptake inhibitors.

Tips for safe use:

• Start with the lowest effective dose.

• Take melatonin 1–2 hours before your target bedtime.

• Avoid taking it in the middle of the night.

• Use it consistently, especially during winter months.

• Combine this with other treatments like light therapy for the best results.

Common side effects:

• Feel sleepy during the day

• Headaches

• Vivid dreams

• Dizziness

• Stomach discomfort

Some people use melatonin during seasonal changes, especially in winter, to support sleep and circadian rhythm balance. Some people may only need it for a few weeks, while others benefit from using it throughout the entire winter season.

Signs it may be time to stop or adjust melatonin:

• Trouble sleeping continues despite consistent use

• You feel overly sleepy during the day

• Mood does not improve or worsens

• Side effects become bothersome

• Symptoms return in early spring or early summer

Melatonin is one option for managing seasonal depression, but other treatments can also support mental health and reduce SAD symptoms.

Light therapy uses a special lamp that mimics natural sunlight. It helps reset the circadian rhythm and reduce symptoms of SAD by lowering increased melatonin production caused by less sunlight.

Tips for using a light therapy lamp:

• Choose a light box that emits 10,000 lux of bright light.

• Use it in the morning for about 20–30 minutes.

• Sit about 16–24 inches away from the lamp.

• Don’t stare directly into the light.

• Use it daily during winter days or when sunlight decreases.

Eating a balanced diet may help boost serotonin levels and reduce depressive symptoms. Foods rich in tryptophan, like turkey, eggs, and oats, support serotonin activity.

Omega-3 fatty acids from fish, walnuts, or flaxseeds may also help regulate mood. Vitamin D, which the body makes from UVB sunlight, may be lower in winter due to less sun exposure. Some studies suggest that supplementing vitamin D could support mood in people with low levels.

Healthy daily routines can reduce the effects of seasonal affective disorder. Regular exercise increases serotonin activity and can improve both mood and energy.

Spending time outside during daylight hours, even on cloudy days, helps reset the body clock. Keeping a consistent sleep schedule and avoiding naps can also support better sleep patterns and reduce the impact of winter blues, helping you stay active and engaged during seasonal changes.

Melatonin is generally well tolerated for short-term and seasonal use, but long-term use for treating SAD should be monitored. It’s important to use the right dose and timing to avoid unwanted effects and ensure it supports your mental health effectively.

Although melatonin is considered safe for most people, some users experience side effects, especially when taken in high doses or at the wrong time. These effects are usually mild and can often be managed with proper usage.

Common side effects and how to minimize them:

• Grogginess: Take melatonin earlier in the evening to avoid feeling sleepy the following day.

• Vivid dreams: Reduce the dosage or adjust the timing if dreams become too intense.

• Headaches: Start with a low dose to see how your body reacts.

• Dizziness: Avoid combining melatonin with alcohol or other sedatives.

• Upset stomach: Take with food if nausea occurs.

Some people should speak with a doctor before using melatonin, especially if they are taking medications or have certain health conditions. Medical guidance is essential when treating SAD alongside other mood disorders like major depression or bipolar disorder.

Consult a doctor if you:

• Are taking antidepressant medication or selective serotonin reuptake inhibitors

• Have a history of bipolar disorder, violent behavior, or suicidal thoughts

• Experience similar symptoms even after taking melatonin regularly

• Have difficulty sleeping or ongoing low mood despite treatment

• Want to know how melatonin fits into your full list of treatment options

Ask your doctor:

• Is melatonin safe with my current medications?

• What dosage and timing would work best for my seasonal pattern?

• Should I combine melatonin with light therapy, vitamin D, or other treatments?

• How long should I stay on melatonin during the winter months?

Melatonin may be one option people explore to support sleep and mood during seasonal affective changes by supporting healthy sleep patterns and regulating the body clock during darker months. While it’s not a cure, melatonin can reduce symptoms like fatigue and low mood when used correctly.

It works best with other strategies, such as light therapy, a balanced diet, and consistent routines. Talk to your doctor before starting melatonin, especially if you have a personal history of mental health conditions or take medications. A personalized plan can make managing seasonal changes easier and improve your overall well-being through the winter season.