Seasonal Affective Disorder (SAD) is a type of depression that people experience in a seasonal pattern or at a particular part of the year. Now, most of us are affected by the changes in seasons, it’s completely normal to feel happier when the sun is out or sleep longer in the winter. However this becomes a problem when the changes in season have a bigger effect on your mood and leads to symptoms of depression. 

It is sometimes referred to as “winter depression” as the symptoms usually come during the winter months but some people experience SAD in reverse, feeling the symptoms in the summer and feeling better during the winter.


The symptoms of SAD are similar to those of depression, but they repeatedly come on during a specific part of the year. There are many symptoms and you don’t need to be experiencing all of them to have SAD. The symptoms include: 

  • Feeling tired, like you have no energy
  • Feeling unable to concentrate or function
  • Sleeping too much or too little 
  • Feeling unable to enjoy the things that you used to enjoy
  • Anxiety (feeling irritable and tense)
  • Withdrawing from friends and family
  • Overeating (particularly comfort eating)
  • A decreased interest in sex or pleasure 
  • Increased drug or alcohol use


The causes of SAD are still unclear, but it is often linked to a reduced exposure to light during the winter months. Theories that set out to explain why some people may develop it include:

  • Lack of light – light sends messages to the part of the brain that controls sleep, appetite, mood, sex drive etc. if there isn’t enough light, these functions are likely to slow down
  • Internal body clock – your body uses sunlight to set it’s internal clock (the time it wakes you up), when there is low light, your internal clock is disrupted, leading to tiredness and depression
  • Melatonin levels – when it is dark, melatonin (the hormone that makes you feel sleepy) is produced but when it becomes light, the production stops. In people with SAD, the body may produce higher levels as there is not enough light to counteract it
  • Serotonin levels – serotonin is a chemical that our brain uses to regulate our mood. People with SAD have been found to have lower levels of serotonin (especially in winter where there is a lack of light), which is linked to depression

How can I help myself?

  • Take advantage of the light available – taking small breaks outside in the day can help you feel better, or even going away to somewhere sunny (if you can afford it) can reduce your symptoms
  • Consider using a light box – these are boxes with fluorescent lights that are made to increase the amount of light that you are exposed to during winter
  • Talk to someone – talking to someone you trust can help in itself, sometimes just sharing your experiences with someone else can make you feel better 
  • Look after your physical health – get some more sleep, choose a healthier diet and do some exercise!
  • Practice self care – find activities that will make you happy and do them. Visit people or places that will make you feel better. Treat yourself! Most importantly, be kind to yourself and treat yourself as you would treat a friend – try not to be hard on yourself on your bad days, it’s a process.


  • Bright Light Therapy – even though you can use a light box to increase exposure yourself, having a more structured course of light therapy with a professional might be more helpful
  • Talking treatments – Cognitive Behavioural Therapy (CBT) focuses on your thoughts, feelings and behaviours and helps you to understand your experiences, teaching you how to recognise and overcome stressful situations. 
  • You may also be offered medication – there are different antidepressants available but you’ll most likely be offered Selective Serotonin Reuptake Inhibitors (SSRIs) to increase the level of serotonin in your brain. It is important that you discuss taking medication with your doctor as you may need to try a few types to find what works best for you

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