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Why Do I Get Sad in the Winter?

Do you ever find that your mood gets low in the winter? The nights are creeping in, the mornings are darker, the weather’s getting colder... if you do, you’re certainly not the only one! In fact, there are some scientific reasons why you might struggle more in the winter.

Seasonal affective disorder (SAD) is a disorder similar to depression, where your mood will get lower during specific seasons [1]. You might get sad, angry, or irritable, or you might have less energy and find it difficult to fall asleep – and you might find it much, much harder to wake up in the morning. This can happen at any time of year, but it’s most common around winter. But why does it happen?

There are lots of theories about the causes of SAD, but the main thing comes down to sunlight. During the summer, the days are longer and sunnier – and the Sun has a major effect on our bodies and brains [2]. When sunlight enters our eyes, it reaches cells called ipRGC cells, which send messages to our brain telling it what time of day it is. This helps us regulate our internal body clock, or circadian rhythm, when tells us when to wake up and when to sleep. When your ipRGC cells begin to register less light, they send messages to your brain letting it know that it’s night time, and to get ready to fall asleep. When this happens, your brain begins to produce a hormone called melatonin, which helps you sleep [3]. As the Sun comes up, and your ipRGC cells register more sunlight, your brain stops producing melatonin, waking you up. In the winter, when there is less sunlight during the day, your brain often produces too much melatonin, making you sleepy and giving you less energy. Getting the right amount of sleep is so important to our mental and physical health, as too much or too little sleep has been linked to health problems such as diabetes and heart disease, and can affect our memory and emotions.

Another hormone affected by sunlight is serotonin [4]. When sunlight enters your eyes, your brain begins to produce this neurotransmitter (a chemical that sends signals between your nerve cells, or neurons), which plays a number of important roles, including healing injuries, helping you sleep, and regulating your mood. When you’re getting less sunlight, your brain often produces less serotonin, meaning that you can feel tired and low.

There are other factors that might affect your mood, too. We know that spending time outdoors and doing regular exercise can have a positive affect on our mental health [5]. When we exercise, our brains produce chemicals including endorphins, which may have a role in making us happier and more energised. Scientists have also found that spending two hours a week in nature improves our mental well-being- when it’s cold and wet, we’re far less likely to spend much time outside, leading to feeling cooped up and unhappy.

Now we know why we get sad in the winter, surely there must be something you can do about it! Here are our top tips for looking after your mental health in the winter months.

1. Get enough Vitamin D

Vitamin D encourages serotonin development, as well as keeping your muscles and bones healthy. It’s very hard to get enough vitamin D from food alone, and instead the best source of vitamin D is – you guessed it – sunlight. In the winter, it can help to take vitamin D supplements, or try to eat food high in vitamin D, such as oily fish and eggs.

2. Get outside

Yes, even when it’s raining! Get your waterproofs on and try to soak up some sunlight every day, even if it’s just for fifteen minutes. If you really can’t face the elements, sitting next to a window can help too. Take a look at our free Nature and Wellbeing fact sheet to find out more about the mental health benefits of getting outside.

3. Exercise

There are plenty of types of exercise you can do indoors during the winter, if you’re not feeing brave enough to go for a run in the rain. Why not try yoga or at-home workouts, or get together with friends for an indoor sport session?

4. Light therapy

For those who are really struggling, getting a UV or SAD lamp can help a lot [6]. These lamps simulate sunlight and encourage your brain to produce more serotonin and less melatonin, giving you more energy during the day and helping you sleep better at night.

5. Get enough sleep

Sleeping in the winter can be difficult, so it’s important to go to bed early and wake up on time. Try to avoid using screens an hour before you go to bed, as the bright light produced by phone, laptop, and tablet screens can trick your brain into thinking it’s daytime and stop it producing melatonin at the right time [7].

[1] What is seasonal affective disorder (SAD)? - Mind

[2] How Light Can Reset Your Circadian Rhythm | Sleep Cycle

[3] About melatonin - NHS (

[4] Serotonin: Functions, Normal Range, Side Effects, and More (

[5] Nature: How connecting with nature benefits our mental health | Mental Health Foundation

[6] Treatment - Seasonal affective disorder (SAD) - NHS (


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