Seasonal Affective Disorder: Can Light Therapy Treat SAR?


Every winter, I get a brief respite after the sad gray days of New York and at 4:30 pm sunsets by visiting my parents in Florida for a few weeks. The suburbs of Florida is not a very interesting or exciting place, but there is something positive about seeing palm trees and a blue sky in December that gives the impression of living.

On my last trip. I have sympathized with a friend from Montreal who, like me, feels inexplicably slow the colder months. He suggested I buy a "happy lamp", a bright light often used to treat seasonal affective disorder, to help me feel more rested. "I use it every morning and it makes the winter bearable," he told me.

I was skeptical about shining a bright light in my face would make me feel better, even though people do it all the time. And even if it was the case At work, I assumed it was to cure the symptoms of my winter lethargy without addressing the underlying problem.

It turns out that light therapy is actually very effective. Katie Sharkey, Associate Professor of Medicine, Psychiatry and Human Behavior at the Brown University School of Medicine at Alpert, confided that she often prescribed light therapy to patients with SAD. "I think it's very effective," said Sharkey, a specialist in psychiatry and sleep medicine, "but I would recommend that people with depressive symptoms be seen by someone who can collaborate with that." treatment, as you would with a pill or therapy. "

In other words, light therapy works, but you probably should not buy a SAD lamp simply because someone told you to do it at a party.

What is seasonal affective disorder?

To understand how light therapy works, you must first understand the causes of seasonal affective disorder.

As its name suggests, seasonal affective disorder is a "depressive disorder or mood disorder that occurs most often in the winter," Sharkey explained, although psychiatrists also records of patients with summer depression. "It is part of a group of syndromes where mood is affected by the length of the day."

The symptoms resemble those of depression all year and include a persistent low mood, a loss of interest in daily activities, irritability, difficulties in getting up in the morning, a feeling lethargy all day and changes in appetite, which may result in eating too much or too little, but often manifests as cravings for "some more caloric foods". Somewhere between 1.4 and 9.7% of Americans have seasonal depression, higher rates move north.

As Joseph Stromberg wrote for Vox, scientists doubted the existence of SAD, which was first identified in the 1980s and which was initially attributed to insufficient exposure to the sun in winter. The idea, which has since been debunked, is that shorter days lead to excessive production of melatonin, a hormone that regulates sleep-wake cycles, making people sleepy and irritable during the dark months of winter. . This was called the photoperiod hypothesis.

Another theory, the dephasing hypothesis, postulates that, since the sun rises later in the winter, the circadian rhythms of man cease to align with their sleep-wake cycles. In simpler terms, since people tend to wake up every day at the same time, even during the months when the sun rises later, a change in sunrise time can upset their circadian rhythms.

Two new studies, both published last September, suggest another explanation for seasonal depression: a brain circuit that connects the light-sensing cells in your eyes to areas of your brain that affect your mood. A study has revealed this type of circuit in mice; A few weeks later, another study suggested the existence of a similar pathway in humans. "It is very likely that disorders such as seasonal affective disorder involve this pathway," said Jerome Sanes, a professor of neuroscience at Brown University in December.

Samer Hattar, one of the authors of the study on the mouse and the head of the section on light and circadian rhythms at the National Institute of Mental Health, discovered in 2002 a discovery which helps to explain these recent developments. In 2002, David Person, a professor of neuroscience at Samer and Brown, discovered a new type of cell in the eye. Combined with other work on the CAS, this suggests that seasonal depression is caused by a lack of light.

"Before the publication of the cellular paper [in 2002], many people – including me, to be honest – just assumed that the depressive effects of light were [caused by] disruption of the circadian clock, "said Hattar. "They assumed that the sensitivity of this system was similar to that of the circadian system. But now that we have found this circuit completely new, we do not know if the sensitivity of the system is identical to that of the circadian system. We do not know how much light – for humans – you have to shine to activate this mood-enhancing way. "

This does not mean that light therapy is not effective. "People have known for many years that light therapy works," Hattar said. Although scientists are still trying to understand the causes of SAD, there is almost a consensus that light therapy is an effective treatment that could directly treat SAD, not just its symptoms.

SAD lamps work – if you use them properly

Light therapy, or phototherapy, was prevalent long before seasonal affective disorder was considered a real affliction. According to the Circulating Now blog of the National Library of Medicine, this practice was used in ancient times to help balance the moods of a person. It was at the time when doctors thought that all medical problems were caused by imbalances in four body fluids (black bile, yellow bile, phlegm). and blood), a bizarre form of pseudoscience that lasted more than 2,000 years – and was then used to treat a variety of conditions, including psoriasis, lupus, and sleep disorders.

In 1903, physician Niels Ryberg Finsen received a Nobel Prize for his work on the therapeutic and physiological effects of light treatment. A few decades later, solar lamps became commonplace in Europe and the United States for both therapeutic and cosmetic purposes.

In Sweden, where the sun sets around 3 pm in January, light therapy clinics have been a popular way to treat SAD since the 1980s. Writer Linda Geddes wrote for Atlantic in 2017 on some Swedish light therapy clinics , even dressed the patients with all-white clothes and had them sit in whitewashed and light-flooded rooms to treat the winter blues. According to Geddes, light therapy clinics are not as prevalent as they were in the 1980s, and there are only a few left today.

But people who suffer from winter-induced depression have other treatment options that do not require sitting in blindly white rooms. Light boxes, or light therapy lamps, have become increasingly popular in recent years, particularly in the United States, and even among people for whom the CAS has not been officially diagnosed.

According to Google Trends, Google searches for "lamp for seasonal affective disorder" have exploded since 2016 – perhaps unsurprisingly, people tend to buy these products in November and December, and Northerners to winters rigorous, like Minnesota and Michigan, are the ones that generate the most search traffic. The Cut, the Wirecutter and CNN have compiled a list of the best SAD lamps, ranging from stylish light boxes that sit on your desk to floor lamps.

Sharkey, the psychiatrist at Brown University, said light therapy could be a very effective treatment for patients with SAD, adding that Hattar's and Sanes' respective studies were a breakthrough in understanding how TAS works. The mouse study, she said, was "probably the most exciting document I've seen in the past year."

"This is huge because it provides a neural substrate for what we have observed clinically" – this natural light can have a huge effect on a person's mood, especially in winter. "The artificial light in which we find ourselves does not give the same signal to our brain as the light we get on the outside," Sharkey told me. "Although it may seem slightly less brilliant than the outside light, it is actually much less bright for our brain. I am sitting in my office now: I can see perfectly, I can read. But if I went outside, even if the weather was covered here, the orders of magnitude were always brighter to the brain, "she said.

Light therapy can more or less induce your brain to think that natural light strikes you as long as you use the right device. "There are some characteristics that you absolutely must look for," she said. "I usually tell people they want a light box with a UV filter that can produce between 1,000 and 5,000 watts. I tell patients that a broad-spectrum light box, rather than one with a particular color or tint, is generally preferable because people tend to find it more enjoyable. These are some of the features that I look at. If you [find one that meets] these three criteria, so it can be based on the aesthetic preference and the price range. You can spend $ 300 or $ 50, and you should spend the number of dollars you can afford.

But, Sharkey warns, the light boxes must be used properly. Use it too early in the day and you will feel tired before bedtime. use it too late and you will have trouble going to bed – and they can cause other side effects, such as headaches, interference with certain medications and rashes. And, she added, this decision should be made in consultation with a professional.

"I urge people who are depressed enough to seek treatment," she said. "It's a rule to follow: take care of your sanity."

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