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A Functional Medicine Protocol for Seasonal Depression

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A Functional Medicine Protocol for Seasonal Depression

Depression is a mental health condition that affects 25 million Americans annually. Seasonal depression is a subtype of depression characterized by changes in how we think and feel that correlate with seasonal changes. At least 5% of Americans are affected by seasonal depression for 40% of the year. However, the numbers are actually expected to be higher than this due to undiagnosed cases. This article will discuss a functional approach to seasonal depression and the many effective therapeutic options for relieving depression symptoms.


What is Seasonal Depression?

Seasonal depression, or seasonal affective disorder (SAD), is a type of depression marked by seasonal changes. Most who experience SAD notice increased sadness at the end of fall or the beginning of winter (known as winter depression). A milder version of winter depression is called the "winter blues," where you might notice feeling down during shorter, darker, and colder days. A smaller percentage of people experience summer depression, a change in mood during the spring and summer. (1, 2)

SAD generally presents during adulthood, between the ages of 18 and 30, and affects more women than men. You may be at higher risk for SAD if you or a family member has been diagnosed with another mental health disorder, such as major depressive disorder, bipolar disorder, ADHD, anxiety, panic disorder, or an eating disorder. Additionally, people living at latitudes far north or south of the equator, where there is less sunlight, are more commonly affected by seasonal depression. (1, 2)

Although it is not known for certain, several hypotheses about the causes of SAD exist, involving hormonal changes and sunlight deficit. We know that sunlight helps to regulate hormonal levels of serotonin (a neurotransmitter that regulates mood) and melatonin (a hormone that regulates circadian rhythm). Reduction in light exposure during the winter months can result in lower levels of serotonin and higher levels of melatonin, both linked to depressed mood. Serotonin synthesis depends on vitamin D availability, primarily derived in the human body from sunlight exposure. Therefore, reduced exposure to sunlight lowers vitamin D levels and can contribute to suboptimal serotonin levels. (3)

Seasonal Depression Signs & Symptoms

Signs and symptoms of SAD may include (4):

  • Feeling sad all or most of the time
  • Feeling hopeless or worthless
  • Thinking about suicide or self-harm
  • Losing interest in hobbies and other activities that used to be enjoyable
  • Fatigue
  • Difficult concentration
  • Problems with sleep
  • Changes in appetite and weight
  • Body pain

Symptoms typically more specific to winter depression include (5):

  • Oversleeping
  • Craving high-carbohydrate foods
  • Weight gain
  • Fatigue

Symptoms specific to summer depression include (5):

  • Insomnia
  • Loss of appetite
  • Weight loss
  • Increased irritability, agitation, and anxiety

Labs That Help Personalize Treatment for Seasonal Depression


Over 20 different nutrient deficiencies have been linked to depression, including B vitamins, zinc, selenium, magnesium, iodine, copper, calcium, and vitamin D. A micronutrient panel is a comprehensive functional nutritional evaluation that can detect suboptimal nutrient levels and deficiencies and evaluate cellular imbalances with micronutrient utilization. If cost is an issue, then priority should be given to measuring vitamin D, given that deficiency is a leading contributor to the development of SAD. A CBC and CMP are also cost-effective panels that can indicate signs of other nutrient deficiencies.


Hormones can be measured through blood, urine, and saliva. This Sleep and Stress Panel measures the daily cortisol and melatonin secretion patterns. Imbalances in either or both of these hormones can cause changes to the biological clock and contribute to SAD.

Other hormones influence mood and brain activity as well. Measuring sex and thyroid hormones can provide additional clues as to why a change in mood has occurred.


A urinary test can measure neurotransmitters, their precursors, and breakdown products to determine how neurotransmitter levels' imbalances may contribute to changes in brain activity, emotions, and energy levels.

An organic acid test (OAT) can assess neurotransmitter status and detect vitamin, amino acid, and antioxidant deficiencies that may disrupt healthy nervous system function.


Variations in our genetics can influence how the body makes and metabolizes hormones and genetically predispose us to mood disorders. Genetic testing can screen for these polymorphisms to target pharmaceutical and nutritional interventions to an individual's needs.

Functional Medicine Treatment for Seasonal Depression

The conventional approach to treating seasonal depression includes a combination of antidepressants, light therapy, and psychotherapy (8). While some people may require pharmaceutical antidepressants to manage their depression, alternative natural interventions can treat symptoms, reduce medication dosages, and, in some cases, prevent the need for pharmacotherapy altogether.


Generally speaking, an anti-inflammatory diet is associated with decreased risk of all forms of depression. When following an anti-inflammatory diet, you want to increase your intake of certain foods while reducing others.

  • Increase intake of fruits, vegetables, whole grains, fish, olive oil, low-fat dairy, and antioxidants.
  • Limit intake of red and/or processed meats, simple carbohydrates, sweets, and high-fat dairy

The most common nutritional deficiencies seen in patients with mental health disorders are omega-3 fatty acids, B vitamins, minerals, and certain amino acids. Understanding this can guide dietary choices that provide the nutrients required for healthy hormonal and neurotransmitter synthesis and signaling. (6)

Proteins are built from amino acids, some of which must be supplied through the diet. Amino acids play many roles in the body, including neurotransmitter synthesis. Protein, and amino acid, deficiency can result in insufficient neurotransmitter levels and exacerbate depressive symptoms. Tryptophan is the amino acid precursor of serotonin (6). Incorporating the following tryptophan-rich foods into your diet can optimize serotonin levels:

  • Poultry
  • Cottage cheese
  • Eggs
  • Avocado
  • Brown rice
  • Sesame seeds, pumpkin seeds, peanuts

Carbohydrates trigger the release of insulin, which promotes the entry of sugar and tryptophan into the brain. Carbohydrates with a lower glycemic index are more likely to provide a lasting effect on brain chemistry and less likely to cause peaks and dips in blood sugar (6).

Aim to incorporate the following carbohydrates into your diet:

  • Whole fruits and vegetables
  • Beans
  • Brown rice
  • Steel-cut oats
  • Whole grain pasta

Omega-3 fatty acids are essential fatty acids that the body cannot make and must be consumed through the diet. Omega-3s are required for brain function and cell growth, and many studies demonstrate the benefits of omega-3 intake for mood. The two key omega-3 fats needed for brain health are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which can be obtained through diet or supplements. (6)

  • The best sources of omega-3 fats are fatty fish like salmon, sardines, mackerel, and trout (7).
  • The best vegan sources of DHA and EPA are seaweed and algae (7).
  • Flaxseeds and pumpkin seeds contain alpha-linolenic acid (ALA), which the body can convert into EPA and DHA; however, this conversion process can be inefficient, so it is not recommended to rely solely on ALA to meet your omega-3 needs (7).

The body requires adequate amounts of other nutritional cofactors to support hormone and neurotransmitter production (7). Vitamins and minerals you want to emphasize in your diet include:

  • B Vitamins (especially vitamin B6 and folate): whole grains, meat, poultry, fish, eggs, dairy, nuts, beans, seeds, dark green leafy vegetables
  • Vitamin C: citrus fruits, tomatoes, bell peppers, kiwi, strawberries, broccoli
  • Vitamin D: salmon, sardines, swordfish, cod liver oil, fortified dairy
  • Magnesium: nuts, seeds, soybeans, black beans, bananas, spinach, broccoli, whole grains
  • Zinc: oysters and other shellfish, meat, poultry, pumpkin seeds, lentils, dairy
  • Iron: red meat, oysters, liver, dark leafy greens, legumes, molasses, tofu

Complementary and Alternative Medicine

Several randomized control trials indicate that artificial bright light therapy can reduce or induce remission of SAD within one to four weeks of starting treatment in 60% of patients. Dawn stimulation is another type of light therapy that can be administered early morning during the last few hours of sleep to mimic the natural sun-rising pattern. It can be used independently or in combination with bright light therapy. (8)

Many herbs in supplemental and whole-food forms can be just as effective as antidepressants at alleviating depression symptoms. St. John's wort, saffron, lavender, and passionflower are among the most studied and effective herbs in depression treatment. (4)

Regular exercise has been shown to ease depression by releasing mood-enhancing neurochemicals, increasing social interaction and self-confidence, and acting as a healthy coping mechanism for negative thoughts. Participating in physical activity for at least 30 minutes three to five days a week improves depression symptoms. (9, 10)

Acupuncture, massage, and aromatherapy are alternative modalities shown to treat depressive symptoms successfully. They can all be safely implemented in conjunction with pharmacotherapy and nutraceutical interventions.



Seasonal depression affects many Americans annually and is thought to be caused by biochemical changes due to vitamin, neurotransmitter, and hormonal balances caused by lack of sunlight. SAD can significantly impair the quality of life in those it affects, causing both mental/emotional and physical symptoms. Working with a functional doctor, you can personalize medical interventions to target identified imbalances in nutrients, neurotransmitters, and hormones contributing to SAD to reverse SAD and live a fulfilling life.

The information provided is not intended to be a substitute for professional medical advice. Always consult with your doctor or other qualified healthcare provider before taking any dietary supplement or making any changes to your diet or exercise routine.
Learn More

Lab Tests in This Article


1. Seasonal Affective Disorder. National Institute of Mental Health (NIMH).

2. Seasonal Depression (Seasonal Affective Disorder). Cleveland Clinic.

3. Munir, S., & Abbas, M. (2022). Seasonal Depressive Disorder. StatPearls Publishing.

4. Henry, K. (2023, February 21). An Integrative Medicine Approach to Depression. Rupa Health.

5. Seasonal affective disorder (SAD) - Symptoms and causes - Mayo Clinic. (2021, December 14). Mayo Clinic.

6. Rao, T.P., Asha, M.R., Ramesh, B.N., et al. (2008). Understanding nutrition, depression and mental illnesses. Indian Journal of Psychiatry, 50(2), 77.

7. Food for the Brain. (2022, November 30). Food for the Brain Foundation.

8. Avery, D. (2022, September 1). Seasonal affective disorder: Treatment. UpToDate.

9. Depression and anxiety: Exercise eases symptoms. (2017, September 27). Mayo Clinic.

10. Cooney, G., Dwan, K., Greig, C. et al. (2013). Exercise for depression. The Cochrane Library, 2013(9).

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