As the days grow shorter and darker in autumn and winter, many people experience a drop in mood and energy that goes beyond the ‘winter blues’.
This is known as seasonal affective disorder (SAD) – a form of depression linked to seasonal change.
Understanding its causes, recognising the symptoms early and seeking appropriate treatment can make a significant difference.
Symptoms often begin in late autumn, worsen through winter and lift again in spring and summer.
Causes
SAD is largely triggered by reduced exposure to sunlight, which disrupts the body’s internal clock and affects the production of key brain chemicals such as melatonin (which regulates sleep) and serotonin (which affects mood).
These imbalances can lead to low mood, fatigue and difficulty concentrating.
The disruption in circadian rhythm can also alter sleep and appetite patterns, making daily functioning harder.
Who’s at risk
SAD is more common in people living in regions with shorter daylight hours, such as the UK.
Research shows that around one in five people in northern climates experience symptoms of SAD.
The condition is also more prevalent in women and tends to run in families, suggesting a genetic component.
People with a history of depression or bipolar disorder are also at higher risk.
Symptoms
Symptoms of seasonal affective disorder mirror those of depression but are strongly tied to seasonal changes. These include:
Persistent sadness or low mood
Loss of interest or pleasure in usual activities
Fatigue or low energy
Feelings of worthlessness or guilt
Difficulty concentrating
Changes in appetite or weight
Sleeping too much or too little
Suicidal thoughts in severe cases
SAD can make socialising, working, or studying feel overwhelming.
Treatments
Seasonal affective disorder is common and treatable.
Light therapy
One of the most effective and widely recommended treatments for SAD is bright light therapy, which uses a special light box to replicate natural sunlight.
Studies show that about half of people using light therapy experience significant improvement in symptoms.
Experts advise using a 10,000-lux light box for 20–30 minutes each morning, ideally within an hour of waking up.
Medication
Healthcare professionals may prescribe antidepressants, particularly SSRIs (selective serotonin reuptake inhibitors), to help regulate serotonin levels and alleviate depressive symptoms during the darker months.
Exercise
Regular physical activity can be as effective as medication for mild to moderate depression.
Just 20 minutes of exercise three times a week can boost serotonin production and improve mood.
Whenever possible, exercising outdoors in daylight can further enhance the benefits by increasing exposure to natural sunlight.
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Cognitive Behavioural Therapy (CBT)
CBT helps people identify and challenge negative thought patterns that worsen depression.
It has been shown to be effective in both treating and preventing the recurrence of SAD symptoms. Combining CBT with light therapy often yields the best results.
Staying connected, maintaining routines, and maximising exposure to daylight can also help lift mood and build resilience through the darker months.
