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2019-01-01 / OnCall

Seasonal Symptoms

Shorter days mean less sunlight — and can mean less vitamin D.


An estimated one billion people worldwide have vitamin D deficiency or insufficiency. Individuals at high risk for vitamin D deficiency include those living far from the equator, those with medical conditions (such as depression, obesity, liver disease, celiac and renal disease), the elderly and those with darker skin.

Low blood levels of vitamin D are often found in people with Seasonal Affective Disorder (SAD). SAD is a sub-type of depression that comes and goes with the seasons, typically starting in the late fall and early winter and going away during the spring and summer. The reduced level of sunlight in the fall and winter months makes vitamin D deficiency more common than at any other time of the year. Several theories exist linking SAD to changing levels of vitamin D3 in the body, which in turn may affect serotonin levels in the brain.

People with SAD experience some combination of the following symptoms during the fall and winter: loss of pleasure or interest, fatigue, guilt, worthlessness, sleep disturbance, depressed mood, suicidal thoughts, carbohydrate craving, increased appetite, excessive sleepiness and weight gain. Of these symptoms, the last four listed seem to be unique to SAD when compared with traditional depression.


A diagnosis of SAD can be made after two consecutive occurrences of depression that occur and end at the same time every year, with the symptoms subsiding during the remainder of the year.

There continues to be much debate in the medical community over the utility of vitamin D testing and treatment. The U.S. Preventive Services Task Force, an independent volunteer panel of national experts in prevention and evidence-based medicine, recommends against routine screening because of the lack of well-established thresholds for vitamin D deficiency as well as lack of impact on health outcomes. That being said, in patients with SAD and low levels of vitamin D, there is some good quality evidence of benefit with vitamin D supplementation. For people who suspect they may be suffering from SAD, taking 800IU of vitamin D daily during the winter months is a reasonable initial option. However, if these conservative measures don’t prove effective, you develop suicidal thoughts, or your symptoms seem to be worsening, please see your primary care doctor to discuss other medical forms of treatment for SAD.

While experts debate whether supplements are necessary or helpful for most healthy people, eating more vitamin D-rich foods is one way to help boost your levels. Salmon, eggs, fortified milk, cod liver and mushrooms are a few rich vitamin D food sources.


Dr. Trevor S. Smith, DO, FAAFP is a board-certified physician specializing in family medicine. He attended the Philadelphia College of Osteopathic Medicine, where he earned his medical degree. He completed his residency at Scott Air Force Base, where he also served as chief resident. Dr. Smith is certified by the American Board of Family Medicine.

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