Light Therapy for Seasonal Affective Disorder

Overview

Seasonal Affective Disorder (SAD) is a mental health condition that refers to depression that occurs at specific times of the year. Most commonly, the symptoms occur in the autumn and winter months and resolve in the spring and summer. This is likely due to less daytime light in the winter months which can impact our hormone levels.

Symptoms are the same as those for depression, including low mood, fatigue, and loss of enjoyment. There are a few treatments that may work such as psychological therapies, light therapy, and antidepressants. Light therapy involves the use of a light box to increase the amount of light we receive in the winter months. Please continue reading to learn more about the use of light therapy for SAD.

Understanding seasonal affective disorder

Background

Seasonal Affective Disorder (SAD) is a mental health condition involving symptoms of low mood that recur at specific times of the year, for 2 or more years. The symptoms are often worse in autumn and winter and tend to resolve in spring and summer.¹ Our exposure to light decreases in the winter months as our days become shorter.

This means we may leave for work in the dark, and return home also in the dark. Depending on our workplace, this leaves very little room for natural light exposure. SAD is thought to occur more commonly in northern latitudes where there is significantly reduced light in winter months.² It is important to note that some individuals may experience SAD the opposite way around, with symptoms occurring in the summer months and resolving in the winter period.

Symptoms

The symptoms of SAD overlap with other mental health conditions such as anxiety and depression. The symptoms must have a seasonal connection over a timeframe of 2 years. This can lead to a delayed diagnosis of SAD. Symptoms include:

• Low mood
• Loss of enjoyment
• Fatigue
• Difficulty concentrating
• Difficulty sleeping 
• Poor eating habits²

This can lead to knock-on effects on work, relationships, and self-care. If you are experiencing any of these symptoms it is important to seek a healthcare professional's advice for diagnosis and discussion of treatment.

Cause

SAD is more common in women and can run in families with a potential genetic element.² It is more common in those who live in northern latitudes due to reduced light in the winter months.² There are a few theories on the cause of SAD, including:

• Increased melatonin production - melatonin is a hormone that is released in the dark and helps us with sleep. These levels are likely higher in those experiencing SAD^1,3
• Circadian rhythm influence - our body has a natural body clock called our circadian rhythm. Our circadian rhythm is heavily influenced by light. This natural rhythm influences our hormones and therefore, our energy levels^1,3
• Lower serotonin levels - serotonin is a hormone that helps us feel happy. Light can help the production of serotonin. The levels of serotonin can be lower in those experiencing SAD^1,3

Current treatments for SAD

Treatment is beneficial to help prevent recurrence every year.^1,2 Treatment is mostly the same as for other low-mood conditions such as depression. Treatment includes:

• Lifestyle change - exercise and a healthy diet are recommended to stay on top of low mood.^3,4 It is useful to maximise the amount of natural light you are in contact with, for example, sitting near windows whilst working or getting outside for a walk
• Psychological therapies - talking therapies such as cognitive behavioural therapy (CBT), counselling, or psychotherapy may be useful to help seasonal low mood. CBT works by reflecting and challenging styles of thinking and can be delivered through individual or group sessions^1,2
• Antidepressants - antidepressants can be useful for some individuals with symptoms of low mood that are severe and impact everyday life.¹ Some antidepressants such as sertraline act by increasing serotonin to lift mood. Antidepressants can take up to 6 weeks to be effective and may cause side effects such as nausea and anxiousness. Once started, antidepressants are continued for at least 6 months following symptom improvement
• Light therapy - light therapy can be incorporated into a daily routine using a lightbox. Details on light therapy will be discussed in more detail below
• Melatonin or agomelatine - these medications have been researched in relation to SAD prevention by adjusting the natural body clock cycle and therefore helping to regulate sleep patterns. The effectiveness of these medications for the prevention of SAD is not clear⁵

Treatment for SAD should be discussed with your GP who can make the right diagnosis, prescribe medication or refer you to talking therapies. Alternatively, you can self-refer for talking therapies through the NHS website.

Understanding light therapy

What is light therapy?

There are different types of light therapy including bright white light, infrared, and dawn simulation.¹ Light therapy can be delivered through a light box which provides much brighter light than regular light bulbs. Lux is a measurement of brightness that can be used to understand light therapy.^1,3 The recommended lux for light therapy is around 5000 lux a day, with the time of exposure depending on the strength of the lightbox.¹ Some may find sunrise clocks beneficial as they can help stimulate a natural wake-up despite dark mornings.

How does light therapy work?

There are a few theories on how light therapy works, including:

• Reduced production of melatonin - this means there will be less of the hormone that makes you feel tired^1,2
• Circadian rhythm influence - this is because light can help regulate the natural body clock¹
• Increased production of serotonin - exposure to light may increase a hormone that makes you feel happy¹

How to use light therapy?

Light therapy can be provided at home using a light box or a light visor. The light does not need direct eye contact but should still hit the eye.¹ Light boxes can be purchased online but it is important to check it is medically approved and safe for use in SAD. This is because approved lightboxes for SAD need to be bright enough to have an effect, whilst also having a special filter to ensure there are no damaging UV rays making contact with the eyes or skin. 

Most find light therapy to be more effective in the morning, as this is more like the natural light cycle.¹ It is important to find a routine that works best for you as others may find light therapy more effective in the evening.¹

Benefits and risks

The evidence for light therapy treatment is varied but light therapy can be shown to be effective for short-term treatment. Evidence shows the effectiveness of light therapy for the prevention of SAD is limited and often of low quality.¹ It may be the case of trialling a few different treatments before finding what works best for symptoms of SAD.

Light therapy has limited reported side effects but some may find that bright light can lead to eye strain, agitation, or headaches.¹ Light therapy may not be recommended if you already have an eye condition or if you have a sensitivity to light, such as due to migraines. Certain medications such as antibiotics or antipsychotics can increase your sensitivity to light. To use safely, follow recommended instructions, speak to a healthcare professional, and monitor any side effects. 

Summary

In summary, seasonal affective disorder is a mental health condition involving seasonal low mood. In SAD, the mood is often worse over autumn and winter but starts to improve in spring. It may be difficult to diagnose SAD until it is clear the symptoms have a seasonal pattern over a couple of years. Lifestyle changes, antidepressants, and talking therapies can all be beneficial to help symptoms of low mood. Lifestyle changes include maximising the amount of natural sunlight in your daily routine. 

Light boxes can also be an effective form of treatment to help combat low mood during the darker winter months. These are thought to be effective in short-term treatment as light can influence your levels of melatonin and sertraline, the hormones that influence mood and sleep. It can often be trial and error before finding the best combination of treatments. If you are struggling with any of these symptoms, it is important to get professional advice and guidance before starting treatment.