Every season has its high points: Spring brings flowers. Summer is associated with sunshine, and fall has brisk temperatures with pumpkin spice everything. And then we get to winter.
In many parts of the world, winter means cold temperatures, shorter days and longer nights. And while many embrace snow days, winter sports, and cozy evenings by the fireplace, earlier sunsets and shorter days means that we have to adjust to fewer hours of sunlight. And that can disrupt our circadian rhythms and lead to a decline in mood or contribute to SAD (seasonal affective disorder), a type of depression.
Light and dark are the major signals that regulate our circadian rhythms. When the retina is exposed to light, that signal affects neurotransmitters that regulate mood and alertness. A lack of light exposure can disrupt those rhythms.
Seasonal affective disorder (SAD) is a type of depression that affects up to 10 percent of the population in northern latitudes; for many people, it lasts for 40 percent of the year.1-3 SAD is characterized by its predictable pattern of depression symptoms that occur during the winter, including:
In someone who suffers from SAD, there is a typically a spontaneous remission of these symptoms in the spring. SAD is commonly accompanied by altered sleep patterns, food cravings, overeating, and weight gain.1
Disrupted circadian rhythms due to the change in season contribute to SAD, and also likely contribute to non-seasonal depression, too. Altered sleep patterns are a common symptom of both depression and SAD. Neurotransmitters, such as serotonin and dopamine, have 24-hour rhythms, and alterations in circadian genes are linked to depression and other mood disorders.4,5
Because circadian rhythms affect the regulation of mood in the brain, many people experience mild depressive symptoms during the winter, even if they are not severe enough to be diagnosed as SAD. Since these seasonal changes are predictable, we can be proactive to prevent a winter decline in mood. Here’s how:
Nature makes people happy, so take a walk. With the right clothing and heat gear, you can bundle up and get outside.
Expose your eyes to bright light, especially in the morning. With the right clothing and heat gear, you can bundle up and take a walk outside soon after waking up. Or use a therapeutic light while you read the newspaper or email, or while eating breakfast. If using a therapeutic light, sit 12-18 inches away for about 30 minutes early each morning throughout the winter.1 Light therapy is an excellent tool for anyone who experiences sadness, fatigue, or disrupted sleep patterns during the winter months.
Research suggests that patients with SAD produce melatonin – the hormone that makes us sleepy – for a longer period of time each night during the winter compared to people without SAD. In the morning, blue wavelengths from sunlight enter the retina and act as a circadian signal, telling the body it is daytime: time to reduce melatonin synthesis and boost serotonin synthesis.6 Therapeutic lights mimic full-spectrum sunlight. Bright light increases alertness and suppresses melatonin synthesis, and light therapy is a first-line treatment for SAD and also helpful for non-seasonal depression.1,6-8
In addition to the effects on neurotransmitters and the circadian system, getting outdoors and feeling sunlight on the skin is a pleasurable experience for most people. This may be due to production of a mood-enhancing substance (beta-endorphin) by skin cells in response to sunlight.9 Of course, be sure to protect your skin appropriately from UV sun damage.
Related: Sun Exposure and Protection: Position paper (free for members)
American Family Physician: Seasonal Affective Disorder
Bright Light as a Personalized Precision Treatment of Mood Disorders
The efficacy of light therapy in the treatment of mood disorders: a review and meta-analysis of the evidence
Beneficial effects of UV radiation other than via vitamin D production
If you’ve ever had a single night of trouble sleeping, you know that inadequate sleep has negative effects that affect your mood, your level of alertness throughout the day, your appetite and much more. Here are some sleep habits to adopt right now:
Synthesis of melatonin and serotonin – a neurotransmitter associated with feelings of well-being – are related, and their balance regulates circadian rhythms. In bright light conditions, more serotonin and very little melatonin is released. In low light or dark conditions, a greater amount of melatonin and a somewhat smaller amount of serotonin is released.10
Adequate sleep allows the brain to work at its best. Sleep promotes learning, memory formation, emotion and stress processing, and good cognitive performance.11-13 Lack of sleep dramatically affects our emotional state, with negative emotions intensified and positive emotions diminished.13
Follow a Nutritarian diet. A diet high in vegetables, fruits, and other plant foods has been linked to psychological well-being, and a lower risk of depression in several studies.14-17 In contrast, a diet low in vegetables may compromise sleep quality.18
Your diet should consist of a wide variety of colorful vegetables and fruits daily, including
Consumption of fast food and commercial baked goods is linked to an increased risk of depression.19 Falling into the traps of boredom and desire for comfort foods can lead to weight gain and also result in a low nutrient intake. This problem is heightened in the current climate, when we’re spending more time at home and can be tempted to snack mindlessly. All this has negative effects on our physical and mental health.
When it’s cold, perhaps salad doesn’t seem quite as appealing as it does when the weather is warmer. But it’s important to eat both raw and cooked vegetables – at least a pound of each – every day. A nut or seed based dressings as well as adding some beans boosts your salad’s satiety factor – plus you’ll want to pair it with a soup or chili to round out your main meal of the day.
Certain vitamins, minerals, and other nutrients are critical to the proper workings of the brain and production of neurotransmitters. Oxidative stress and chronic inflammation – the same food-related culprits for heart disease, cancer, and diabetes – are linked to depression and negative mood states. Phytochemical-rich foods have antioxidant and anti-inflammatory effects, and some – flavonoids for example – may help to normalize neurotransmitter levels.20-29
Vegetarian diets are associated with healthy mood states: a cross-sectional study in Seventh Day Adventist adults
Diet quality and depression risk: A systematic review and dose-response meta-analysis of prospective studies
Dietary flavonoid intake and risk of incident depression in midlife and older women
Fast-food and commercial baked goods consumption and the risk of depression
Relationship of homocysteine, folic acid and vitamin B12 with depression in a middle-aged community sample
Impact of dietary folate intake on depressive symptoms in young women of reproductive age
The role of dietary polyphenols on adult hippocampal neurogenesis: molecular mechanisms and behavioural effects on depression and anxiety
Natural products, micronutrients, and nutraceuticals for the treatment of depression: A short review
Antidepressant Flavonoids and Their Relationship with Oxidative Stress
Even an ideal, plant-rich diet may not supply optimal amounts of certain nutrients. That’s why I recommend that anyone following a Nutritarian eating style should take safe multivitamin and a vegan omega-3 fatty acid supplement to ensure that they get adequate amounts of brain-supporting vitamins, minerals, and fatty acids that are difficult to get from plant foods (zinc, vitamin B12, vitamin D, DHA, and EPA). For those looking for additional support, Mood Balance Biotect combines the benefits of three of the most effective supplements for natural mood management: saffron, 5-HTP and SAMe. Clinical trials on each of these three natural substances suggest they promote a healthy, positive mood.
Zinc helps to limit oxidative stress in the brain, and vitamin B12 is important for neurotransmitter synthesis.30,31 Vitamin D is thought to affect the production of neurotransmitters, including serotonin.32 Low intake of zinc, B vitamins, or vitamin D has been associated with increased risk of depression,30,33-37 and depression is a known symptom of B12 deficiency.30,36
Either have your vitamin D level tested, or take 50 mcg (2000 IU) vitamin D3 daily if you aren’t sure of your blood vitamin D. I recommend maintaining a blood vitamin D level (25(OH)D) in the 30-45 ng/ml range. Supplementation with vitamin D has improved depression symptoms in several studies.38
The omega-3 fatty acids DHA and EPA are important components of brain cell membranes, and research links adequate amounts of DHA and EPA to lower risk of depression.39 The research suggests supplementation, especially with EPA, helps improve depression symptoms.40-42 I recommend most healthy adults take a DHA-EPA supplement (preferably algae-derived rather than fish-derived), since levels are likely to be low for most who don’t eat omega-3-rich fish regularly.
B Vitamins and the Brain: Mechanisms, Dose and Efficacy-A Review
Zinc in the central nervous system: From molecules to behavior
Efficacy of vitamin D supplementation in major depression: A meta-analysis of randomized controlled trials
Role of omega-3 fatty acids in the treatment of depressive disorders: a comprehensive meta-analysis of randomized clinical trials
The cold weather makes most of us want to curl up under a blanket on the couch. Sure, it’s fine to “chill and Netflix” as long as you’re not skipping walks and workouts! Make sure you’re sticking to your usual physical activity schedule, because exercise is nature’s mood elevator. Regular exercise is linked to a reduced risk of depression and is an effective component of treatment for depression.43-46
Exercise works by increasing the mood-elevating neurotransmitter serotonin, increasing the production of “neurotrophic factors” – brain chemicals that promote neuron (brain cell) growth and survival, reducing inflammation, improving connections between neurons, and improving blood flow in the brain.47,48
The natural brain-healthy properties of a high-nutrient diet, regular exercise, adequate vitamin D and omega-3 stores, and light exposure combine to promote a positive mood, even in the cold, dark days of winter.