More than the "winter blues": understanding the science behind seasonal affective disorder (SAD)

As we head into the winter months in the midst of a global pandemic, ensuring we support one another to keep on top of our mental health is vital.

Whether we like it or not, summer is now behind us. The days are getting shorter and the nights are getting longer.

In previous years, the dread of a long, cold winter was often counterbalanced by the excitement of the upcoming holiday season and the promise that a new year brings. But amid unprecedented job losses, social distancing, and growing cases of coronavirus, the winter of 2020-21 feels markedly different. For many of us, the thought of spending a winter under COVID-19 restrictions is more than just a daunting prospect.

Far from simply being the "winter blues," seasonal affective disorder (SAD) is a serious mental health problem that often goes untreated. This World Mental Health Day, it's time we removed the stigma and recognised this critical public health problem.

What is seasonal affective disorder?

SAD is a form of clinical depression that affects people as the days get longer, darker and colder during the winter months. Prior to the outbreak of coronavirus, SAD was thought to affect 6% of adults in the UK and 5% of adults in the US. With rates of depression doubling during the COVID-19 pandemic, these figures for this year are expected to be even higher.

Typical symptoms of SAD include:

  • Anxiety
  • Cravings for carbohydrates
  • Feelings of despair, guilt and hopelessness
  • Insomnia
  • Irritability
  • Lethargy

Though milder than other forms of depression, SAD can also occasionally lead to major depressive episodes or serious suicidal thoughts. If you find yourself persistently thinking suicidal thoughts, you should reach out to a health professional immediately.

Why do we get SAD?

Most theories link SAD to circadian rhythms. Decreased exposure to bright light during the autumn and winter can — in SAD sufferers — drive the production of melatonin, which subsequently drives the lethargy and depressive symptoms commonly associated with the condition.

The morning sun is our natural alarm. When our eyes detect sunlight, a signal is sent to the suprachiasmatic nucleus — our circadian clock. It informs our pineal gland to inhibit the secretion of melatonin. If there is no light when we wake up in a morning, it tricks our brain into thinking that it’s still night time. This also explains why we get tired earlier during winter months.

It is unsurprising to discover that in countries closer to the poles, such as Canada and Norway, the percentage of people who get SAD is higher. In Alaska, for example, where days are endlessly dark in the winter, occurrences of SAD in the population can reach up to 10%

Serotonin deficiency

Production of serotonin is also thought to have an impact on seasonal affective disorder. Studies show that serotonin, a neurotransmitter that regulates mood, may also be modulated by light.

Though we don’t know exactly how reduced sunlight leads to lower levels of serotonin, there are increasing numbers of studies seeking to discover the direct link. According to the Pfizer blog, Breakthroughs, brain scan studies indicate 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.”

The gender divide

Interestingly, women tend to get SAD at much higher rates than men. About 80% of people who suffer from seasonal affective disorder are women between the ages of 18 and 45. This could be related to hormonal differences between the sexes.

However, some researchers suggest that SAD is a remnant of adaptive behaviour to protect pregnant women in the winter months during the last Ice Age. According to Robert Levitan, Professor of Psychiatry at the University of Toronto:

“Ten thousand years ago, during the ice age, this biological tendency to slow down during the wintertime was useful, especially for women of reproductive age because pregnancy is very energy-intensive. But now we have a 24-hour society, we’re expected to be active all the time and it’s a nuisance. However, as to why a small proportion of people experience it so severely that it’s completely disabling, we don’t know.”

Another impact could be that — despite increasing awareness of mental health issues — men are less likely to consult with a mental health practitioner, which could skew the numbers somewhat. Whatever the reason, SAD is an issue that — as far as we know — predominantly affects women.

Light therapy

For both melatonin and serotonin, the best treatment for most people with SAD is light therapy. As light cues get weaker deep into the winter, a common solution is to use a light box for 30 minutes at a time which imitates natural light — allowing the body clock to recalibrate. Most people respond well to this non-invasive therapy.

Some countries are tackling the issue head on. Sweden, for example, which sees very little natural light during winter months, has converted bus stops to emit light which can help to treat SAD.

For people who feel blue in the winter months, rather than those with SAD, simply exposing yourself to light by having a walk in the middle of the day can have a positive effect. Whether done every day, or a few times a week, exposure to natural light can give you the mood boost necessary to overcome the symptoms of SAD.  

Tips for managing SAD

Thankfully, there are several steps we can take to regulate our mental health during these difficult months. Mental health experts suggest the following:

  1. Daylight walks
  2. Artificial lights
  3. Healthy eating
  4. Regular exercise
  5. Regular sleep
  6. Maintaining virtual or socially distanced connections
  7. Talking therapies such as cognitive behavioural therapy (CBT)

If you feel like you are suffering from SAD or any other mental health issue, please seek advice from your nearest medical professional.

For more insights into the ever-changing world of STEM stay tuned to the SRG blog.

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