We woke up to a dull morning, after some rain during the night. As I was making our morning salad, the sun came out and a big smile lit my face. I declared, “The sun is out, I am already in a good mood” to which my husband stated “Light cannot measure mood”. That was all I needed as a challenge. I know my husband is a knowledgeable scientist, and when he says something with strong conviction, it is usually based on solid research. Yet I also know that recently, I’ve been more tuned in to the latest in mood research. So, I decided to search for empirical evidence of the influence of light on mood, and whether light can actually serve as a measure of our mood.
Light and colour in general have been repeatedly shown to influence people’s mood, both at a biological and psychological level. From a biological point of view, “cool” light can influence the circadian rhythm, and as such the mood. Research done in work places and schools in the 1980’s showed that the use of cool light can increase the productivity of workers significantly, as well as students’ ability to concentrate. Apart from physical effects, it can also affect mood and thus productivity. Exposure to natural light is especially beneficial. Natural light from both morning and evening has been found to decrease depression and improve mood, energy, alertness, and productivity.
Temperature of light, measured in Kelvin (K), is a numerical measurement of the color of light emitted when an object is heated to a high temperature. As the temperature increases, the object changes colors. Counterintuitively, lower color-temperature light sources are called “warm” because they emit red, orange and yellow, whereas higher color-temperature light sources are called “cool” because they are on the violet and blue end of the color spectrum. The ambient light of a typical sunny day is about 5,000~5,500K and is considered cool. If you don’t have access to daylight, studies have also found that working under “blue-enriched” light bulbs that are 17,000K actually increases work performance by supporting mental acuity, vitality, and alertness while reducing fatigue and daytime sleepiness. Researchers at the University of Greenwich found in a two-month study that the workers they put under “blue-enriched light bulbs” reported feeling “happier, more alert and had less eye strain.” Most studies agree that natural light from both the morning and evening has been found to decrease depression and improve mood, energy, alertness, and productivity.
In late fall and winter, shorter daylight hours leave many people with little to no sun exposure, signaling the brain to create too much of the sleep-regulating hormone melatonin. This overproduction of melatonin leads to seasonal affective disorder (SAD) , a mood disorder that affects an estimated 10 to 20 percent of the population. Historically, researchers have considered women to be more likely to experience seasonal depression. But psychiatrists are increasingly finding that’s not the case. “The classic crying and melancholic depression are more the norm of expression in women. But men express things differently, showing depression with more irritability, anger or frustration,” said Dr. Andrew Angelino, director of psychiatry at Howard County General Hospital.
In the beginning of the 90s I had a client who was doing well in therapy, and was hoping to pursue her studies at the university. However, people say what they think but act on what they feel. At the beginning of December, she declared that she thought therapy was no longer helping. To understand what brought on this change, I questioned what she really felt, and found out that every year a feeling of darkness and heaviness would start in December, and then she would go into a state of depression that left her unable to function. She thought that therapy would help her, and so far it had addressed a lot of her difficulties, but perhaps there was still something unresolved, and she did not know if she could go on. I suspected SAD, and gave her some literature about it. All the symptoms fit. The research that we found recommended sitting under special “blue enriched” lightbulbs for 6 hours every day. This is both an expensive and time-consuming solution. Then I remembered a friend who was a neurochemistry physician and scientist, who told me once about his research in the field. He’d investigated the use of vitamins in treating SAD when he worked for a large drug company. He found promising results with the use of large doses of niacinamide. His paper, which he shared with me, explained that niacinamide is necessary to reduce melatonin during the day. The body can only convert niacin into niacinamide when cool light (i.e. sunshine) enters the eyes. When winter comes, and we do not get enough cool light from the sun (e.g. from staying more indoors), the level of melatonin rises and literally puts us to sleep and brings on the feeling of depression. His solution, which was rejected by the drug company since it could not be patented, was to take very large amounts of slow release niacinamide, so that the level in the body would mimic the level existing during the summer.
The problem was, I am not licensed to prescribe, and the large doses that were recommended were nowhere to be found in Canada. The client’s GP agreed to give the prescription after reading the paper, so we were now looking for a source. Lo and behold, we found one! A health-food store in Port Huron (US) carried time-release niacinamide in 1000mg tablets. No, they could not deliver them to Canada. So, we started a clandestine operation. I had a colleague and friend in Sarnia, on the Canadian side, who would go over the border to do some shopping for herself, and bring back the coveted product. My client started with one tablet a day for a week, increased to 2 tablets, and by the third week, with 3 tablets her mood started changing dramatically. No side effects, so she took the full recommended dose for her weight, 4 tablets per day. She was symptom free, cheerful, and back to school. When spring came, and then summer, she gradually decreased the dose, and increased it again with the onset of winter. She was able to function well, finished her university studies, and when I met her years later, she was still doing well.
I know this is not proof, it is only anecdotal, and I have no idea if a full double-blind study was ever done, but it is certainly cheaper, simpler, and more convenient than the light-bulb solution. I did find an interesting article Light Affects Mood and Learning through Distinct Retina-Brain Pathways, published in Cell, Sep. 2018 by Diego Carlos Fernandez, et al. The researchers found two different pathways for delivering the light from the retina to the brain. One path led to a previously unrecognized thalamic region, involved with mood-regulating centers. The other pathway led to the hippocampal learning area. They claimed that “Together, these results provide new insights into the neural basis required for light to influence mood and learning”.
Was my husband right by saying “light can not measure mood”? I guess it depends on what question he was answering. My statement was that the light was affecting my mood. So, the question I was answering was “Can light affect your mood?” I think I found out that the clear scientific answer is yes. Not only does light affect mood, but it also affects learning ability. My husband’s question seemed to be “Can light be used as a measure of mood,” and his answer was no. However, recently someone actually looked at this question again, and it looks like there actually is a new development that may allow the use of light as a proxy to measure our mood. In 2011 Ditte Svane-Knudsen reported about a Danish experiment in Sciencenordic. Researchers used a sophisticated wristband which registered and measured the light every 30 seconds to examine the impact of light on each subject’s state of mind. In an extensive study, researchers for the first time made use of objective measurements to investigate how much – or little – truth there is in my husband’s belief. Each of the study’s 900 participants wore a sophisticated wristband for a week. The wristband measured the amount of light and participants’ levels of physical activity. Since the researchers were not named in the article, I could not find the results of the experiment. My choice now is to accept my husband’s statement, or to remain with his question unanswered in my mind, and keep searching. One thing is clear, though: light does affect mood.