Seasonal Affective Disorder; Winter depression, explained

The changes in seasons can affect us in profound ways, some people report feeling more cheerful when the days are longer, and the sun is shining. While others crave carbohydrates during the long, often grey UK winters. 

If you are you dreading the clocks going back next month and the long cold dark evenings ahead. Or remember how you wanted to want to hibernate and overeat last winter, you might you be at risk of winter depression.  The medical term for winter depression is Seasonal Affective Disorder which is shortened to SAD, September is the month to take action, read on for help.

For people who experience SAD, the change in seasons has a much more significant effect on their wellbeing, energy levels and mood, sometimes with considerable impact on their daily life. 

SAD is a recognised mental health disorder, symptoms can vary as in other types of depression, but it’s the repeating pattern that helps to identify people at risk. Symptoms usually appear as soon as the days get shorter and are at their most severe between December and February. For most people, symptoms improve or disappear in the spring and summer, but return around the same time each year.

SAD facts

  • It can affect anyone living in the northern hemispheres
  • It is rare in those living within 30 degrees of the equator, where daylight hours are long, constant and bright.
  • SAD can begin at any age, but the main onset is between 18-30 years of age.
  • It may hereditary and affected children and adolescents too.
  • In UK, Europe, Australia and Canada, doctors estimate that at least 5% of the population suffers from SAD.

SAD Symptoms 

Symptoms of SAD can vary as in other types of depression, but it’s the repeating pattern that helps to identify people at risk. Symptoms usually appear as soon as the days get shorter and are at their most severe between December and February. For most people, symptoms improve or disappear in the spring and summer.

Signs and symptoms of SAD can include:

  • A persistent low mood, or irritability
  • Loss of pleasure or interest in normal everyday activities
  • Feelings of despair, guilt and worthlessness
  • Lethargy (lacking in energy) 
  • Disturbed sleep and early morning awakening.
  • Sleeping for longer than normal and finding it hard to get up in the morning
  • Needing a nap in the afternoon
  • Craving carbohydrates and gaining weight
  • Concentration and memory problems
  • Anxiety, tension or stress that is harder to manage

SAD is an often misunderstood illness, with affected people sometimes attributing their symptoms to stress or other lifestyle factors. One of the most important distinguishing features of SAD is that aid it is seasonal, symptoms disappear in spring, depending on the intensity of sunlight this can be a sudden or gradual improvement.

What causes seasonal affective disorder (SAD)

The exact cause of SAD is not well understood, it’s often linked to reduced exposure to sunlight during the shorter autumn and winter days. Compared to the 19th century when 75% of the population worked outdoors. Less than 10% of the people work in natural outdoor light or get access to enough daylight which has resulted in a dramatic increase in light deficiency symptoms. The main theory is that a lack of sunlight in winter reduces the efficient function of the hypothalamus gland in the brain which in terms affects the following:

  • Melatonin, the hormone that makes us sleepy; the body may produce it in higher than normal levels in people susceptible to SAD.
  • Production and levels of serotonin, a hormone that affects mood, appetite and sleep, a lack of sunlight may lead to lower serotonin levels, which affects mood.
  • The circadian rhythm or internal clock. The body uses sunlight to time various important functions, such as when we wake up, so lower light levels during the winter may disrupt the body’s internal clock and lead to symptoms of SAD.
  • It’s also possible that some people may have increased vulnerability to seasonal affective disorder because of a previous trauma, a stressful event such as childbirth, redundancy or bereavement, longterm illness or due to genetic factors.

Help and treatment

SAD can be a disabling illness preventing people from functioning without extended medical treatment. Your GP should be your first port of call, they will access your wellbeing and mental health, asking about your mood, lifestyle, eating habits sleep patterns, plus any seasonal changes in your thoughts and behaviour. Or they may use a paper or online assessment tool with multiple choice Q&A which can be a helpful way of assessing the severity and longevity of your symptoms. Two or more consecutive winters of symptoms needed to confirm a diagnosis of SAD.

Tip: Take a list of your symptoms and consider booking a double appointment.

Treatments for SAD

Several treatments are available for SAD, including lifestyle measures, medication and light therapy, you need to use these from September

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.


Antidepressants can be helpful but can take four to six weeks to take full effect. They are most effective if taken in the autumn before the symptoms appear, and continued until spring. Which means if you had symptoms last year, you need to pop along the doctors this month.

Talking therapies 

Cognitive behavioural therapy (CBT) or counselling are NICE recommendations, results vary.

Dawn-stimulating alarm clocks

May also be useful for some people. They brighten the bedroom with gradual increases in light with a 30-minute sunrise timer, which helps to regulate the sleep/wake cycle. Fans report a boost in their mood, energy and productivity levels for the rest of the day.

Lightboxes and light therapy

Some people with SAD find that light therapy can help improve their mood, this involves sitting by a special lamp each morning. The light produced by the Lightbox simulates the sunlight that’s missing during the darker winter months. Lightboxes come in a variety of designs, including desk and wall-mounted fixtures, visors and now glasses. They produce a dazzling light measured in lux, the higher lux, the brighter the light and the less treatment time needed, for example, treatment using 10,000 lux lightboxes can take as little as 30 minutes a day.

Lightboxes aren’t available on the NHS, they are expensive but free of VAT when used for medical use. Some companies will hire them, choose a lightbox produced by an approved manufacturer. Most people can use light therapy, approved medical lightboxes have filters that remove harmful ultraviolet (UV) rays, so there’s no risk of skin or eye damage for most people. However, exposure to bright light may not be suitable for everyone, please check with your GP first. The Seasonal Affective Disorder Association provides a list of recommended manufacturers, click here for details.

How does light therapy work?

Light therapy (phototherapy), encourages the brain to reduce the level of melatonin, the hormone that makes us sleepy. It also increases production of serotonin, the happy hormone,  more about serotonin in the next post.

The evidence is mixed regarding the overall effectiveness of light therapy, some studies have concluded it is useful if used first thing in the morning while others state they are best for short-term results helping relieve symptoms when they occur. If light therapy is helpful, most people notice an improvement in their symptoms within 7 – 14 days.


  • Getting as much natural sunlight as possible, even a brief lunchtime walk can be beneficial
  • During the autumn and winter, making the work and home environments as light as possible. Sit near windows when indoors, or use daylight lamps.
  • Eat a healthy well-balanced diet. East food rich in tryptophan which is an amino acid that helps make serotonin (see the next post)
  • Learn simple relaxation and stress-relieving breathing techniques.
  • Exercise will produce the feel-good hormone serotonin.


Tell family, friends and work colleagues about Seasonal Affective Disorder, and how it affects YOU. They can offer more YOU support if they understand how your mood changes during the winter.


Please note: All entries on this blog should offer information and guidance only. They should not be considered a substitute for medical advice, diagnosis or treatment given in person by a trained health professional.









Latest blogs