Seasonal affective disorder 


Who is affected by SAD?

It's estimated that SAD affects about 2 million people in the UK, and more than 12 million people across Northern Europe.

Like other types of depression, SAD is more common in women than in men, with up to three times more women than men affected.

The symptoms of SAD are most likely to develop in people aged 18 to 30.

Seasonal affective disorder (SAD) is a type of depression that has a seasonal pattern.

The episodes of depression tend to occur at the same time each year, usually during the winter.

As with other types of depression, the two main symptoms of SAD are a low mood and a lack of interest in life. You may also be less active than normal and sleep more.

Read more about the symptoms of seasonal affective disorder

Winter depression

SAD is sometimes known as "winter depression" because the symptoms are more apparent and tend to be more severe at this time of the year.

The symptoms often begin in the autumn as the days start getting shorter. They're most severe during December, January and February.

In most cases the symptoms of SAD begin to improve in the spring before eventually disappearing.

What causes SAD?

The exact cause of SAD isn't fully understood, but it's thought to be linked to reduced exposure to sunlight during the shorter days of the year.

Sunlight can affect some of the brain's chemicals and hormones. However, it's not clear what this effect is. One theory is that light stimulates a part of the brain called the hypothalamus, which controls mood, appetite and sleep. These things can affect how you feel.

In people with SAD, a lack of sunlight and a problem with certain brain chemicals stops the hypothalamus working properly. The lack of light is thought to affect the:

  • production of the hormone melatonin
  • production of the hormone serotonin
  • body's circadian rhythm (its internal clock, which regulates several biological processes during a 24-hour period)

Read more about the effects of sunlight on melatonin, serotonin and the body's circadian rhythm.

Diagnosing SAD

You should visit your GP if you have the symptoms of SAD. They may carry out an assessment to check your mental health.

Your GP may ask you about your mood, lifestyle, eating habits and sleeping patterns, plus any seasonal changes in your thoughts and behaviour.

Read more about diagnosing seasonal affective disorder.

Treating SAD

As with any type of depression, SAD can be difficult to live with. It can make you feel tired, stressed and unhappy. However, it can usually be treated successfully.

Light therapy is often used to treat SAD. It involves sitting in front of or beneath a light box that produces a very bright light. Light boxes come in a variety of designs, including desk lamps and wall-mounted fixtures.

You should speak to your GP and read the manufacturer's instructions before using a light box to treat SAD.

Depending on the nature and severity of your symptoms, talking therapies such as cognitive behavioural therapy (CBT) or medication such as antidepressants may also be recommended.

Your GP will recommend the most suitable treatment programme for you, which may involve using a combination of treatments.

Read more about how seasonal affective disorder is treated.

Page last reviewed: 19/11/2013

Next review due: 19/11/2015


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maym said on 12 September 2014

I haven't been to the doctors as I know my doctors won't take me seriously. I don't have mental health issues or depression of other sorts but I do have SAD. I have suffered for years. I have even been able to borrow and use a light box but found it didn't work. I now just get my husband to turn all the lights on before he leaves work. Waking up to the lights on is not perfect but compared to them not on, there's no contest. This is my only solution if I am to get out of bed every morning on time. I don't have lamps but I guess you set them up on timers. Give it a go.

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jf007 said on 09 July 2014

I've had SAD for a few years, and tried the lightbox. Haven't used CBT (anyone tried it?). Currently using 5htp patches. Perhaps moving to Spain is the real cure...

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gossy said on 28 May 2014

I am a suffer of sad and have been since 1990, currently on citalopram, I get really low in the winter my symptoms start in late October and reach a peak at Christmas where i eat more and feel lethargic, tearful and just don't want to do anything, once I see the longer days my mood lifts into a sunnier happier mood, more patience and I am better to be around, I have had therapy on the nhs, and tried a sad lamp, the latter didn't do anything for me.
I do find my my sad returns on the dull rainy days of spring summer, when we get a prolonged bad spell, such has now, like the previous writer said, the amount of blue skies, to dull cloud effects my mood levels, has I write I feel very tired and down, sad is more recognized has a winter illness, due to lack of daylight, but I find even in the summer, lack of brightness effects me the same, not being able to get into the garden or outside apart from getting wet through.

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PaulShipston said on 14 May 2013

I have suffered from SAD for many years and am aware of the influcence that the time of year and weather have on my general mood.

I have found it useful to separate the impact of SAD into two parts.

Firstly, there is the seasonal trend in daylight. We know that the number of hours of daylight each day follows a fixed annual cycle. We know exactly how many hours of daylight that we will receive today, tomorrow, and so on. I find that a high degree of certainty is helpful in managing and minimising the impact of SAD.

Secondly, there is the weather. Weather is very difficult to predict and whilst it follows some general seasonal trends, we do not have the same degree of certainty around the type of weather we will experience each day like there is with the number of hours of daylight.

It is very obvious to me that my mood is affected by the amount of cloud vs. blue sky and the brightness level. There is a significant difference in the level of brightness when walking down the street on a clear blue sky and warm sunny day compared to a cool, cloudy, drizzly, winter day.

I have found a lightbox to be very helpful in the past and more recently I received Cognitive Behaviour Therapy free on the NHS, as part of a wider treatment of clinical depression, which was excellent.

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Russell S said on 04 May 2013

I lived in hot sunny climates in Africa and Australia from the early 80's to the early 2000's and was mostly positive and happy while in warmer climates. Since moving back to the U.K in 2002 I have noticed the negative and depressing symptoms- particularly since 2009.

I notice a lot of people in the U.K are cranky and snappy ,angry or miserable. The UK weather and less happy society in the UK has affected me more over the last few years...I concluded my mental and physical health was primarily being thrown around by the poor U.K weather quite a bit. I often feel tired and sleep long hours in winter. I also have lower back pain and prescribed co-codamol which doesn't help with SAD in winter.

But in the summer I feel almost O.K - although I don't think I've seen a good summer since 2009 because the UK weather has been verrry lousy in past years. I enjoyed the heatwave of 2003 when it got up to 38 degrees because that's what I was used to. I could imagine a lot of people who lived in sunnier climates and came to the UK also miss the heat and the sun, and probably people like me who lived long periods in the sunnier climates notice that we get SAD syndrome because we can compare the positive life we used to have in warmer sunnier climates...

Not only does SAD make a person less active and sleepy, it slows the metabolism considerably, and I have put on 20kg's of weight in the U.K since 2002! I eat more, sit around more and don't feel the positive spark that I used to have as a younger person. I noticed my parents also have become more depressed in winter months but become more positive in the summer.

SAD syndrome is a nasty thing to be affected by, and perhaps far more people should be made aware of just how the weather affects the brain chemistry, metabolism and personality. I was diagnosed with symptoms of chronic depression in February- It's now May and I feel the symptoms lifting slightly...

Let's hope for a good summer...

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Scottigirl said on 30 January 2012

In restrospect, I think my mother suffered from SAD, winters being darker and longer in Scotland and I have negative memories of that time. I believe I also suffer but don't think GPs take this syndrome seriously enough simply because it is seasonal and will pass. Probably sufferers put it down to "the weather" or the "time of year" and just put up with it. Few of us can afford to pay for light therapy or CBT.

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taraoke said on 19 November 2011

Actually, "Pedantic but true", what is written by the NHS is correct. Some people suffer from SAD in the summer, it's just not as frequent.

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Pedantic but true said on 27 October 2009

"SAD affects most people in the winter."

This means that the majority of people suffer from SAD in the winter.

I think what you meant to say was

"SAD affects people most in the winter"

or "Most people who suffer from SAD are affected in the winter."

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