Seasonal Affective Disorder (SAD)

Oct 01, 2020

It's the time of year when the weather turns, heralding darker nights and shorter days. This may affect your mood and, in some instances, trigger Seasonal Affective Disorder. Dr Eddie Murphy explains.

Seasonal Affective Disorder (SAD) is a type of depression that is related to changes in seasons. It begins and ends at about the same times every year. If you are like most people with SAD, your symptoms start in the autumn and continue into the winter months, sapping your energy and making you feel moody.

Around 2-10% of Europeans and North Americans are affected by SAD, three quarters of whom are women (although both genders are affected equally in older age). 60% of those suffering from SAD get it to varying degrees every winter, which is a lot of months feeling gloomy. Given that there is a lot of crossover between SAD and other forms of depression, it is always wise to discuss any feelings of low mood with your GP to help you get the appropriate support and treatment you may require.

Where does SAD come from?

The specific cause of SAD remains unknown. Some factors that may come into play include:

  1. Your biological clock (circadian rhythm): the reduced level of sunlight in autumn and winter may cause winter-onset SAD. This decrease in sunlight may disrupt your body’s internal clock and lead to feelings of depression.
  2. Serotonin levels: a drop in serotonin, a brain chemical (neurotransmitter) that affects mood, might play a role in SAD. Reduced sunlight can cause a decrease in serotonin, which may trigger depression.
  3. Melatonin levels: the change in season can disrupt the balance of the body’s level of melatonin, which plays a role in sleep patterns and mood.
SAD is diagnosed more often in women than in men, and SAD occurs more frequently in younger adults than in older adults. Factors that may increase your risk of SAD include:

  1. Family history: people with SAD may be more likely to have blood relatives with SAD or another form of depression.
  2. Having major depression or bipolar disorder: symptoms of depression may worsen seasonally if you have one of these conditions.
  3. Living far from the equator: SAD appears to be more common among people who live far north or south of the equator. This may be due to decreased sunlight during the winter and longer days during the summer months.


Treatment for SAD may include light therapy (phototherapy), medications and cognitive behavioural therapy (CBT).


We know that a lack of light causes SAD and that people with SAD need much more light to function normally than others do. It is not surprising, therefore, that the primary treatment for SAD is bright light. It has been proven to be effective in up to 85% of people diagnosed with SAD.

Lightboxes are devices that come in all different sizes and designs. The user sits in front of the lightbox, so that bright light enters the eyes. Light treatment has to be used every day in winter to enable people with SAD to lead a normal life. When treatment starts, it usually takes three to four days to work, but the effect wears off if it is not used for three to four days.

Treatment should start in early autumn, ideally before symptoms start, and continue until spring. It can also be used on dull, cloudy days in summer. Light levels in Ireland are very changeable, and some people can be affected by a prolonged downturn in the weather. Although the worst time is inevitably mid-winter, a wet June can sometimes be worse than a sunny February, so be adaptable.

Light therapy is a mainstay treatment for SAD at the moment, and a really useful website is If you cannot access light therapy, try to make your days as bright as possible. Work next to a window, have lights and lamps on at home and spend as much time as possible outdoors. Beware that people with macular degeneration, retinal disease, or photosensitive skin conditions or medications should not use light therapy. Seek advice from your doctor if you are unsure.


Drug treatments for SAD can be used in combination with light therapy. They can also be used alone, which is particularly useful for those who do not respond to light treatment. Your GP prescribes all drug treatments.

Cognitive behavioural therapy

CBT allows people to talk about the impact of SAD and can assist people with SAD to make positive, constructive changes to their daily winter routines. It may help them to feel better about the fact that they need to adapt to winter, rather than attempt to carry on regardless. They may begin to feel less guilty or frustrated if things are not the same as they are at other times of the year.

Finally, embrace ‘hygge’ 

Learn about hygge (pronounced ‘hooga’), which originated in Scandinavian countries where they barely see daylight for weeks. SAD is a significant problem in such regions, but inhabitants tackle this by embracing the concept of hygge. In essence, it means creating a warm atmosphere and enjoying the good things in life with family and friends. Rather than resisting, it is sometimes easier to go with the flow. So embrace the winter, the lights, fires,  and wrapping up warm.

Symptoms of SAD

  • Mood changes: low mood, feelings of hopelessness (especially on the topic of winter, saying things like “I can’t stand this” or “I hate winter”), withdrawing or avoiding social events, irritability, and decreased enjoyment from life or hobbies.
  • Sleep changes: usually oversleeping, extreme tiredness and napping, although some people may also get insomnia or sleep disturbances.
  • Appetite changes: overeating is common and, in particular, an intense craving for carbohydrates or sugary foods. You may find yourself putting on weight over winter. Some people may, however, get a decreased appetite.
  • Concentration: trouble focusing, forgetting things, and difficulty finishing tasks.
  • Physical symptoms: low energy, muscle tension or pain, decreased sexual drive, stomach aches and headaches, and a sensation that your body is heavier or harder to move than usual, and sluggishness.

Members and students can contact CA Support on 01 637 7342 or 086 024 3294, by email at or online at

Dr Eddie Murphy is a clinical psychologist, mental health expert and author.