Seasonal affective disorder (SAD): How early sunsets can have a biological effect on our mental health – Dr Gwenetta Curry

Light therapy, exercise, vitamin D supplement, cognitive behavioural therapy and other forms of treatment can help people with seasonal affective disorder

Now that the festive season has come to an end and a new year has arrived, many people are faced with the challenge of making it through the rest of the generally cold, dark, and wet winter months. While some enjoy the gloomy weather, for others the lack of sunshine causes feelings of depression.

Seasonal affective disorder (SAD) usually lasts around five months with January and February being the most severe months for those who experience symptoms. Winter SAD is a type of depression characterised by a recurrent seasonal pattern. Some of the most common symptoms consist of oversleeping, anxiety, over-eating, and social withdrawal. The NHS estimates that about one in 15 people experience SAD across the UK.

The further from the equator people live, the more common condition. Suggested treatments include light therapy, psychotherapy, antidepressant medication, and vitamin D supplements.

For some, short days can lead to depression but help is available (Picture: Peter Thompson/Heritage Images/Getty Images)

Some people have found that light therapy can be an effective way to treat their symptoms. Light boxes simulate sunlight which can fill the gap during the dark winter months. It is thought that the light may encourage your brain to reduce the production of melatonin and increase the production of serotonin, a chemical that carries messages between nerve cells in the brain and body and which plays an important role in mood, sleep, digestion, nausea, wound healing, bone health, blood clotting, and sexual desire.

Light therapy is practiced by sitting in front of a light box for about 30 minutes, usually in the morning, to boost your mood for the day. The recommended light boxes have filters that remove the harmful ultraviolet rays so there is no risk of skin or eye damage for most people. As with any treatment, there may be risks due to underlying conditions or medications, so it is important to consult your GP.

Scientists have linked vitamin D deficiency to an increased risk of winter-pattern SAD because it is believed to promote serotonin activity. With less daylight in the winter, people with SAD may have lower levels of this vitamin, further reducing serotonin activity.

It acts more like a hormone than just a vitamin and too little can have a major impact on mood disorders. Populations with more melanin in their skin tend to have the lowest vitamin D levels as they will need longer sun exposure to get the recommended amount.

Lastly, experts recommend that SAD be treated in the same way as other types of depression. This would include the use of cognitive behavioural therapy which aims to help identify and explore the ways your emotions and thoughts can affect your actions. Once you identify the patterns, you can learn how to develop new coping strategies.

Exercise has long been used as a method to help boost mood as it increases the levels of endorphins in your blood. The fresh outdoor Scottish air can be rejuvenating but the cold is a clear deterrent for those who prefer a warm climate. If people are experiencing what they feel may be seasonal affective disorder, it is important they make an appointment with their GP to discuss possible treatment options.

Dr Gwenetta Curry is an Edinburgh University reader in race, ethnicity and health