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seasonal affective disorder

What is Seasonal Depression? 


According to the NIMH

Seasonal Affective Disorder (SAD) is a type of depression that comes and goes with the seasons, typically starting in the late fall and early winter and going away during the spring and summer. Depressive episodes linked to the summer can occur, but are much less common than winter episodes of SAD.

General Statistics


National Institute of Psychology Today

  • Seasonal affective disorder is estimated to affect 10 million Americans.

  • Another 10 percent to 20 percent may have mild SAD.

  • SAD is four times more common in women than in men.

  • The age of onset is estimated to be between the age of 18 and 30.

  • Some people experience symptoms severe enough to affect quality of life, and 6 percent require hospitalization.

  • Many people with SAD report at least one close relative with a psychiatric disorder, most frequently a severe depressive disorder (55 percent) or alcohol abuse (34 percent). 

Video: Learn About Seasonal Affective Disorder | UPMC

Do you suffer from SAD? Learn more about the signs and symptoms of Seasonal Affective Disorder and how you can cope in the autumn and fall. Read more:


When I Realized My Depression Was Seasonal

"It took me several years to realize how much sunlight and the seasons affect my mental health. My first episode of major depression began in late fall and eased in early spring, but at the time, that had no significance. I only saw the situational stressors that caused me to become overwhelmed. Increasing pain in my back and hips had caused me to stop dancing, which was my passion, stress release and creative outlet at the time. The frustration of being held back by pain was compounded by vague diagnoses and unsuccessful treatments. After a while of this, I was forced to confront the fact that the pain was not going away and I wouldn’t be able to dance anytime soon."

Coping With S.A.D. Moments During Holidays With Seasonal Affective Disorder

"It’s that time of year: the time when we’re cooking, cleaning and entertaining more than usual. We’re traveling and shopping, all on top of everything else we tend to do every day without fail. It’s also when our days get shorter and our nights longer. And for some of us, that means our eyes are not twinkling and our dimples are not merry. Instead, it can be hard to be excited about anything. All many of us really want to do is wrap up in a cozy blanket with a cup of tea and a good book."

7 Ways I'm Preparing for Seasonal Affective Disorder This Year

"I was trapped indoors for days at a time — unable to drive anywhere because road conditions were so bad. At one point during the winter even going for a walk on our farm was dangerous because of the snow and ice. By the end of the winter I was definitely depressed. All I wanted to do was lay in bed and sleep all day and I had no motivation to do any of the activities that I usually enjoy."

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As the days grow darker and colder, many of us occasionally experience the winter doldrums. A small percentage of the US population (about 1 to 10 percent, depending on where you live), however, suffers a more severe form of the blues known as seasonal affective disorder (SAD), with symptoms such as feeling sluggish, agitated, hopeless, overly fatigued and changes in appetite. In the U.S., the prevalence of SAD is linked to how far north you live. The incidence of SAD is nearly 10 percent of the population in New Hampshire, compared to 1.4 percent in Florida. 

SAD didn’t become a clinically diagnosed condition until the 1980s, when physician Norman Rosenthal moved from South Africa to the United States and noticed that he felt unproductive during the winter months and started to bounce back come spring. In its most severe cases, SAD symptoms are in line with a major depressive episode, where people are severely incapacitated, unable to function and may even have suicidal thoughts. Collaborating with colleagues at the National Institutes of Health, Rosenthal conducted research on how light exposure affected circadian rhythms and pioneered the concept of light exposure therapy. 

An extensive body of scientific research exists today on SAD, yet researchers still can’t definitively explain why this seasonal-related disorder occurs. They have, however, uncovered some clues showing that decreased daylight exposure disrupts circadian rhythm cycles, which in turn impacts levels of key body regulating hormones or neurotransmitters in the brain such as melatonin and serotonin.

A Misaligned Clock

The morning light is truly nature’s alarm clock. Our retinas have special cells called retinal ganglion cells (RGCs) that detect sunlight and send a signal along nerves to a part of the brain known as the suprachiasmatic nucleus, the timekeeper of our circadian rhythms.  The early dawn light sets off a chain of events that tell our internal body clock to send signals to the pineal gland, which inhibits the secretion of melatonin, the hormone that prepares your body to sleep. 

In the winter, as such light cues become weaker, our body clock becomes misaligned and melatonin secretion continues, tricking our bodies into thinking it’s still night time. Interestingly, some people who are completely blind—lacking the photoreceptors responsible for vision—still retain the special light-detecting cells, and can also experience SAD. 

The Serotonin Connection 

Another area of research is dedicated to investigating how SAD is linked to depleted levels of serotonin in the brain, a neurotransmitter that regulates mood. The serotonin connection also helps explain why people with SAD often crave more carbohydrate-rich foods in the winter, which are known to cause a spike in these mood-enhancing chemicals. Researchers have yet to show the crucial link of how diminished daylight leads to a drop in serotonin levels. 

But they have done brain scan studies to show that people with SAD had higher levels of a serotonin transporter protein (SERT) in the winter compared to healthy individuals. The more SERT a person has in his/her brain, the less the mood-enhancing neurotransmitter is freely available, causing people to more likely to experience symptoms of depression.

Simulating Nature’s Light

One common, non-invasive treatment for SAD is to use a light therapy box, which mimics natural outdoor light, and may help people recalibrate their body clocks and relieve symptoms of SAD. In Sweden, which has long stretches of winter darkness, officials have brought light therapy to their citizens by converting some bus stops into UV light therapy boxes. 

We may have coined the term winter blues even before we knew the science behind it, but research is shedding light on how we can keep our mood a bit sunnier even during those long, dark months."


"A number of treatments are available for seasonal affective disorder (SAD), including cognitive behavioural therapy, antidepressants and light therapy.

Your GP will recommend the most suitable treatment option for you, based on the nature and severity of your symptoms. This may involve using a combination of treatments to get the best results.

NICE recommendations

The National Institute for Health and Care Excellence (NICE) recommends that SAD should be treated in the same way as other types of depression.

This includes using talking treatments such as cognitive behavioural therapy (CBT) or medication such as antidepressants.

Light therapy is also a popular treatment for SAD, although NICE says it's not clear whether it's effective.

See NICE guidance about the treatment and management of depression in adults.


Things you can try yourself

There are a number of simple things you can try that may help improve your symptoms, including:

  • try to get as much natural sunlight as possible – even a brief lunchtime walk can be beneficial

  • make your work and home environments as light and airy as possible

  • sit near windows when you're indoors

  • take plenty of regular exercise, particularly outdoors and in daylight – read more about exercise for depression

  • eat a healthy, balanced diet

  • if possible, avoid stressful situations and take steps to manage stress

It can also be helpful to talk to your family and friends about SAD, so they understand how your mood changes during the winter. This can help them to support you more effectively.

Psychosocial treatments

Psychosocial treatments focus on both psychological aspects (how your brain functions) and social aspects (how you interact with others).

Cognitive behavioural therapy

Cognitive behavioural therapy (CBT) is based on the idea that the way we think and behave affects the way we feel. Changing the way you think about situations and what you do about them can help you feel better.

If you have CBT, you'll have a number of sessions with a specially trained therapist, usually over several weeks or months. Your programme could be:

  • an individual programme of self-help

  • a programme designed for you and your partner (if your depression is affecting your relationship)

  • a group programme that you complete with other people in a similar situation

  • a computer-based CBT programme tailored to your needs and supported by a trained therapist

Read more about CBT

Counselling and psychodynamic psychotherapy

Counselling is another type of talking therapy that involves talking to a trained counsellor about your worries and problems.

During psychodynamic psychotherapy you discuss how you feel about yourself and others and talk about experiences in your past. The aim of the sessions is to find out whether anything in your past is affecting how you feel today.

It's not clear exactly how effective these 2 therapies are in treating depression.

Read more about psychotherapy.


Antidepressants are often prescribed to treat depression and are also sometimes used to treat severe cases of SAD, although the evidence to suggest they're effective in treating SAD is limited.

Antidepressants are thought to be most effective if taken at the start of winter before symptoms appear, and continued until spring.

Selective serotonin reuptake inhibitors (SSRIs) are the preferred type of antidepressant for treating SAD. They increase the level of the hormone serotonin in your brain, which can help lift your mood.

If you're prescribed antidepressants, you should be aware that:

  • it can take up to 4 to 6 weeks for the medication to take full effect

  • you should take the medication as prescribed and continue taking it until advised to gradually stop by your doctor

  • some antidepressants have side effects and may interact with other types of medication you're taking

Common side effects of SSRIs include feeling agitated, shaky or anxious, an upset stomach and diarrhoea or constipation. Check the information leaflet that comes with your medication for a full list of possible side effects.

Read more about antidepressants.

Light therapy

Some people with SAD find that light therapy can help improve their mood considerably. This involves sitting by a special lamp called a light box, usually for around 30 minutes to an hour each morning.

Light boxes come in a variety of designs, including desk lamps and wall-mounted fixtures. They produce a very bright light. The intensity of the light is measured in lux – the higher lux, the brighter the light.

Dawn-stimulating alarm clocks, which gradually light up your bedroom as you wake up, may also be useful for some people.

The light produced by the light box simulates the sunlight that's missing during the darker winter months.

It's thought the light may improve SAD by encouraging your brain to reduce the production of melatonin (a hormone that makes you sleepy) and increase the production of serotonin (a hormone that affects your mood).


Who can use light therapy?

Most people can use light therapy safely. The recommended light boxes have filters that remove harmful ultraviolet (UV) rays, so there's no risk of skin or eye damage for most people.

However, exposure to very bright light may not be suitable if you:

  • have an eye condition or eye damage that makes your eyes particularly sensitive to light

  • are taking medication that increases your sensitivity to light, such as certain antibiotics and antipsychotics, or the herbal supplement St. John's Wort

Speak to your GP if you're unsure about the suitability of a particular product.

Trying light therapy

Light boxes aren't usually available on the NHS, so you'll need to buy one yourself if you want to try light therapy.

Before using a light box, you should check the manufacturer's information and instructions regarding:

  • whether the product is suitable for treating SAD

  • the light intensity you should be using

  • the recommended length of time you need to use the light

Make sure that you choose a light box that is medically approved for the treatment of SAD and produced by a fully certified manufacturer.

Does light therapy work?

There's mixed evidence regarding the overall effectiveness of light therapy, but some studies have concluded it is effective, particularly if used first thing in the morning. 

It's thought that light therapy is best for producing short-term results. This means it may help relieve your symptoms when they occur, but you might still be affected by SAD next winter.

When light therapy has been found to help, most people noticed an improvement in their symptoms within a week or so.


Side effects of light therapy

It's rare for people using light therapy to have side effects. However, some people may experience:

  • agitation or irritability

  • headaches or eye strain

  • sleeping problems (avoiding light therapy during the evening may help prevent this)

  • tiredness

  • blurred vision

These side effects are usually mild and short-lived, but you should visit your GP if you experience any particularly troublesome side effects while using light therapy."


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"O’Donnell also says she suffers from seasonal affective disorder, often called SAD, which causes her to feel depressed during the fall and winter. 'Like in The Wizard of Oz, the color goes out,' she says. 'That is what happens in depression. Everything gets gray.'

No one should fear the stigma of taking medication for depression, she says: 'It saved my life.'"

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