Mental health

It’s reached that time of year when the air becomes chillier and the days grow shorter, with many of us want to do nothing more than curl up on the sofa. As outdoor activity becomes less appealing — or even possible if the weather becomes truly foul — it’s only natural to want to hibernate with an endless supply of stodgy puddings.

But for some, the desire to comfort-eat, a lack of energy and an accompanying grumpiness may be caused by more than the drop in temperature.

Seasonal Affective Disorder (SAD) can affect individuals at any time of the year, but is usually associated with winter. Common symptoms, among others, include low mood, disinterest or lack of pleasure in normal everyday activities, tearfulness, lethargy, tiredness and increased appetite.

But we don’t need science to tell us that we’re generally chirpier when it’s sunny. The mental health charity Mind states that in northern Europe an estimated one in ten suffers with SAD, and that the condition is “extremely rare” in countries near the equator where daylight hours are long.

What causes seasonal affective disorder?

SAD is thought to be a result of how sunlight affects our internal body clock (circadian rhythms), and production of the hormones melatonin and serotonin.

Produced by the pineal gland when it’s dark, melatonin makes us sleepy; whereas serotonin, sometimes dubbed the ‘happy hormone’ is a neurotransmitter that carries messages between nerve cells. It is thought that SAD sufferers may have lower levels of serotonin, affecting the efficiency of how the nerve cells communicate, leading to SAD symptoms.

What is bright light therapy?

Although getting out and about during autumn and winter daytime is a positive step, cloudy days still may not provide enough light for some.

Bright Light Therapy (BLT) is one approach to combating winter SAD, in which a light box is used so that bright light hits the retina in the eye, sending nerve signals to the brain. While organisations such as the NHS are hesitant to endorse the treatment as a certainty, it is suggested as a possible solution.

Others are more optimistic. For example, in a study of 22 women diagnosed with both bulimia nervosa and winter SAD, a four-week trial of light therapy, using a 10,000 lux fluorescent light box with an ultraviolet filter for 30 to 60 minutes per day in the early morning, resulted in a significant improvement in mood and a decrease in binges and purges.

Small studies have also shown promising results in using BLT in pregnant women, adolescents and children.

At 200-500 lux, normal office or domestic lighting isn’t sufficient for light therapy. Modern light boxes give out at least 10,000 lux and each treatment session with one should last for between 30 and 60 minutes. Light boxes with a lower lux output may need to be used for longer.

Food and neurotransmitters

For some people, BLT alone may not be enough. The effects of biological changes caused by a lack of sunlight can create a double-whammy in how we nourish ourselves with food. While the urge to eat stodgier, comforting foods can stem from a natural reaction to colder weather, it is thought that the desire for carbohydrates also comes from a need to boost those happy hormones.

Research indicates that sugar consumption causes the release of dopamine, another neurotransmitter, in a ‘reward centre’ in the brain called the ventral striatum. And in a human functional imaging study, sucrose was found to create dopamine activity in midbrain areas, while an artificial sweetener did not.

Dopamine has also been termed a happy hormone or reward drug, impaired availability of which may cause abnormalities in the generation of circadian rhythms in some SAD sufferers. And so, in a vicious circle, low levels of serotonin and dopamine may draw us to more sugary foods as we try to cheer ourselves up. Yet with a less healthy diet and the physical and emotional impact of any weight gain, we may end up feeling worse in the long run.

A less balanced diet could also mean that we take in fewer of the nutrients that might actually help us battle against the very condition that we are trying to stave off.

Can supplements help to manage seasonal affective disorder?

Foods that contain the amino acid tryptophan can help, as tryptophan helps the body produce serotonin. However a diet low in niacin (vitamin B3) may cause tryptophan depletion because when niacin is not available, the liver will convert tryptophan into niacinamide (another form of vitamin B3), but at the expensive rate of converting 67 mg of tryptophan into just 1 mg of niacinamide.

Ingesting more tryptophan and niacin might seem to be the obvious solution, but even that may not be enough because the body naturally produces enzymes that deplete tryptophan.

Tryptophan 2,3-dioxygenase (TDO), is the first enzyme in the tryptophan oxidation pathway and plays a central role in regulating tryptophan levels.

A second enzyme, indoleamine 2,3-dioxygenase (IDO), also specifically breaks down tryptophan and is elevated by infections and viruses, as well as with old age, inflammation, autoimmune disorders and malignancies, so the elderly and infirm may be particularly susceptible to tryptophan depletion.

Topping up tryptophan levels with supplements may not be the answer, however, because high blood levels of tryptophan induce TDO production, which will work to lower them.

Research has looked at how IDO, which will deplete even low levels of tryptophan, might be counteracted. One natural aid may lie in curcumin, derived from turmeric and also known as the food colouring E100, which studies indicate may have a benefit in suppressing IDO.

But even a curry a day would not provide much active ingredient, because only a pinch of turmeric is ever used, about 3% of which would be curcumin. Also curcumin is poorly absorbed through the gut, although one study reported a 200% increase in bioavailability of curcumin if taken with piperine, an alkaloid found in black pepper.

To sum up, what the evidence shows is that while light boxes might benefit some SAD sufferers, there is no one panacea to surviving winter. In addition to continuing outdoor activity as much as possible, a varied diet can be essential to keeping us physically and emotionally well during the long, dark months.

If you enjoyed this article, you might also like reading about the science of gratitude and how to practice it