As colder weather drives us inside, most of us are well-acquainted with the increased spread of infectious diseases like colds, the flu, and COVID-19. But the winter months can also take a toll on our mental health. Find out what conditions could impact your mind during this colder season – and what you can do to break through the fog and take action.
Seasonal Affective Disorder
Many of us are familiar with the “winter blues” that can creep up during the darker, colder months. But did you know that it’s classified as an actual health condition?
Seasonal affective disorder (or SAD), is a type of depression that’s connected to seasonal changes. Most commonly, SAD begins during the winter months and resolves in the summer (though, less commonly, it can also be triggered in the spring/summer and resolve in the winter).
Symptoms of SAD can resemble depression symptoms, such as:
- Often feeling sad or down
- Losing interest in favorite activities or pastimes
- Low energy levels
- Changing eating habits, particularly overeating or craving carbohydrates
- Weight changes
- Feeling worthless or guilty
- Struggling to concentrate or make decisions
- Having thoughts of death or suicide
Vitamin D Deficiency
Vitamin D from the sun can fulfill up to 90 percent of our daily vitamin D requirements.  Our skin absorbs the ultraviolet B (UVB) rays from the sun before kicking off a complex process that makes vitamin D. However, the changing seasons with the Earth’s movement can impact how much vitamin D we can absorb. In cities as far north as Boston, one 1988 study found that human skin did not produce any pre-vitamin D on cloudless days from November to February. 
In addition to causing symptoms such as fatigue and bone, muscle, and joint pain, vitamin D deficiency has also been associated with mood changes and depression. One 2020 literature review covering vitamin D and depression found that, in nine particular studies, depressed individuals had lower vitamin D levels compared to a control group.  This same review also noted that those with the lowest vitamin D levels had the greatest risk of depression.
According to some research, seasonal affective disorder and vitamin D levels may be connected. One 2014 research study hypothesized that vitamin D plays a big role in regulating processes associated with SAD, particularly because vitamin D levels in our nervous system can impact production of feel-good hormones like serotonin and dopamine, along with the function of our circadian rhythm. 
Can light therapy help during the winter months?
For individuals who may struggle with seasonal affective disorder, light therapy is one established treatment that may provide benefits. One 2020 review of 23 studies with 1,120 non-seasonal depressed patients found that light therapy is significantly more effective than other comparative treatments. 
According to the Center for Environmental Therapeutics, individuals can benefit from using light boxes providing 10,000 lux at a distance.  However, it’s important to consult with a therapist to determine what the right light dosage is for your specific situation.
How can I improve my mental health this winter?
Try the following steps if you’re struggling with mental health during the winter season:
- Find activities that can help you get moving during the winter. One 2004 study found that 15 to 30 minutes of exercise, three times per week, helped reduce anxiety and depression. 
- Stay connected with friends, family, or other loved ones.
- Talk to your doctor about practical action steps you can take, such as light therapy or vitamin D supplementation.
- If symptoms do not improve within two weeks, consult a licensed mental health professional.
If you have questions about your wellbeing this winter, at-home health tests can be a great place to get answers. An at-home vitamin D test can help you see if you have a vitamin D deficiency, while a mental vitality DX test can provide a big-picture look at your overall mental wellbeing. Winter can be a challenging time – but you don’t have to wait until the spring thaw to take action and move forward.
 Holick, Michael F. “Sunlight and Vitamin D for Bone Health and Prevention of Autoimmune Diseases, Cancers, and Cardiovascular Disease.” The American Journal of Clinical Nutrition, vol. 80, no. 6, 1 Dec. 2004, doi:10.1093/ajcn/80.6.1678s.  Webb, A. R., et al. “Influence of Season and Latitude on the Cutaneous Synthesis of Vitamin D3: Exposure to Winter Sunlight in Boston and Edmonton Will Not Promote Vitamin D3 Synthesis in Human Skin.” The Journal of Clinical Endocrinology & Metabolism, vol. 67, no. 2, Aug. 1988, pp. 373–378., doi:10.1210/jcem-67-2-373.
 Menon, Vikas, et al. “Vitamin D and Depression: A Critical Appraisal of the Evidence and Future Directions.” Indian Journal of Psychological Medicine, vol. 42, no. 1, 6 Jan. 2020, pp. 11–21., doi:10.4103/ijpsym.ijpsym_160_19.
 Stewart, Alan E., et al. “Possible Contributions of Skin Pigmentation and Vitamin D in a Polyfactorial Model of Seasonal Affective Disorder.” Medical Hypotheses, vol. 83, no. 5, 18 Sept. 2014, pp. 517–525., doi:10.1016/j.mehy.2014.09.010.
 Tao, Long, et al. “Light Therapy in Non-Seasonal Depression: An Update Meta-Analysis.” Psychiatry Research, vol. 291, Sept. 2020, p. 113247., doi:10.1016/j.psychres.2020.113247.
 Center for Environmental Therapeutics. “CET's Basic Guide to Light Therapy.” Center for Environmental Therapeutics, CET.org, 26 Nov. 2021, cet.org/cets-basic-guide-to-light-therapy/.
 Guszkowska, Monika. “Effects of exercise on anxiety, depression and mood". Psychiatria polska vol. 38, no. 4, 2004, pp. 611-20.