Seasonal Affective Disorder and the winter blues

With winter now fully in swing, many people will start to notice a shift in their mood and energy. For some, it’s a mild case of the “winter blues” – a bit more tired, a bit less motivated. For others, it’s something more serious: Seasonal Affective Disorder, or SAD, a recognised form of depression that follows a seasonal pattern.

SAD is more than just disliking cold weather or feeling a bit low. It’s a clinical condition that typically begins in autumn, worsens through winter, and lifts in spring. Symptoms include persistent low mood, loss of interest in activities, low energy, difficulty concentrating, changes in appetite (often craving carbohydrates), oversleeping, and feelings of hopelessness or worthlessness.

It’s estimated that around 2% of the UK population experiences SAD, with a further 10-20% experiencing milder symptoms often referred to as “subsyndromal SAD” or winter blues. The science behind SAD centres largely on light – or rather, the lack of it. Reduced sunlight in winter affects the body’s internal clock, or circadian rhythm, which regulates sleep, mood, and hormone production.

Less light also means lower levels of serotonin, a neurotransmitter that affects mood, and increased production of melatonin, which makes us feel sleepy.

Geography matters too. SAD is more common in northern latitudes where winter days are shortest. In the UK, the difference between summer and winter daylight is stark, and that lack of natural light has real consequences for mental health. Women are also more likely to experience SAD than men, and it often runs in families, suggesting that there may be a genetic component.

The impact of SAD shouldn’t be underestimated. It can affect work performance, relationships, and overall quality of life.

People with SAD often describe feeling like they’re “hibernating” – withdrawing from social activities, struggling to get out of bed, and losing the motivation to do things they usually enjoy. For those already living with depression or anxiety, winter can make symptoms significantly worse.

The good news is that SAD is treatable. Light therapy – using a special light box that mimics natural daylight – is one of the most effective treatments. Sitting in front of a light box for 20-30 minutes each morning can help reset circadian rhythms and boost serotonin levels. It’s important to use a proper SAD lamp (typically 10,000 lux) rather than just any bright light, and to position it correctly for best results.

For some, talking therapies such as cognitive behavioural therapy (CBT) can be helpful, particularly a version adapted for SAD that focuses on managing thoughts and behaviours specific to the condition. In more severe cases, antidepressant medication may be recommended.

Winter doesn’t have to mean months of low mood and fatigue. With the right strategies and support, it’s possible to navigate the darker months with resilience.