A Functional Medicine Protocol for Seasonal Depression

If you or someone you know has ever experienced the winter blues, you're not alone. Seasonal affective disorder (SAD) affects millions of people worldwide, causing symptoms of depression that coincide with changes in seasons. In the United States, 5% of adults experience SAD for about 40% of the year (28).  

Living with SAD can be challenging, but there is hope. This article aims to provide a comprehensive and easy-to-follow outline for healthcare providers to diagnose and successfully treat SAD. By understanding the diagnostic criteria, implementing evidence-based treatment protocols, and incorporating lifestyle interventions, providers can empower individuals affected by SAD to manage their symptoms and improve their quality of life.

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What Is Seasonal Depression?

Seasonal depression, clinically known as seasonal affective disorder (SAD), is a type of depression that occurs at a specific time of year, typically during the fall and winter months when there is less natural sunlight. Some people will get a rare form of SAD called "summer depression," which starts in the late spring or early summer. 

A mild version of SAD is called the "winter blues," where you may feel slightly down during the winter as days get shorter, colder, and darker. Unlike the winter blues, the mood changes associated with SAD significantly impact daily life. 

Seasonal Depression Signs & Symptoms

Symptoms of seasonal depression are similar to those of major depressive disorder (MDD). However, these symptoms tend to recur at the same time each year, lasting for 4-5 months. Symptoms may start mild and increase in severity as the season progresses. (24, 25)

SAD symptoms include: 

• Persistent feelings of sadness, hopelessness, or worthlessness
• Thoughts of self-harm or suicide
• Losing interest in activities that used to be enjoyable
• Social withdrawal
• Fatigue
• Difficulty concentrating or making decisions
• Changes in sleep patterns and appetite
• Unintentional changes in weight
• Body pain

Root Causes of Seasonal Depression

The exact cause of SAD is not fully understood, but it's believed to be related to changes in light exposure, circadian rhythm disruption, neurotransmitter imbalances, and genetic predisposition. In general, these factors have been identified as increasing your risk for SAD:

• Female sex
• Younger age
• Family history of depression
• Personal history of major depression or bipolar disorder
• Geographic location: SAD is more common in populations who live farther away from the equator

Light Exposure

Reduced exposure to natural sunlight, particularly during the fall and winter months when days are shorter and sunlight is weaker, is a significant trigger for SAD. Light exposure affects the body's natural production of vitamin D and melatonin.

Sunlight exposure is essential for the synthesis of vitamin D in the skin. When the skin is exposed to ultraviolet B (UVB) radiation from sunlight, a precursor molecule called 7-dehydrocholesterol is converted into vitamin D3 (cholecalciferol). Insufficient sunlight exposure, therefore, can lead to vitamin D deficiency. 

Serotonin is a neurotransmitter involved in mood regulation. Serotonin synthesis depends on vitamin D availability. Low vitamin D can cause low levels of serotonin, which is correlated to depression.

On the other hand, melatonin is a hormone involved in regulating the sleep-wake cycle. Melatonin production is triggered by darkness and induces a sleepy state, signaling the body it is time for bed. In contrast, people with summer-pattern SAD may have reduced melatonin levels, leading to disrupted and poor-quality sleep. 

Circadian Rhythm Disruption

The body's internal clock, or circadian rhythm, regulates various physiological processes, including sleep-wake cycles, hormone production, and mood. Changes in light exposure can disrupt the circadian rhythm, leading to alterations in sleep patterns, energy levels, and mood regulation. This disruption may contribute to the development of SAD symptoms.

Genetic Predisposition

There is evidence to suggest that genetic factors contribute to the risk of developing SAD. Family studies have shown that individuals with a family history of mood disorders, including depression and bipolar disorder, are more likely to experience SAD. Genetic variations in genes involved in circadian rhythm regulation and neurotransmitter metabolism may influence susceptibility to SAD.

How to Diagnose Seasonal Depression

Diagnosing seasonal depression involves recognizing recurrent patterns of depressive episodes. To ensure accurate diagnosis, health professionals will assess symptoms over at least two consecutive years while ruling out other potential explanations for mood disturbances.

Step 1: Use the DSM-5 Criteria

SAD is recognized as a subtype of MDD in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). The DSM-5 provides specific criteria for diagnosing SAD, which include:

• Individuals must experience recurrent episodes of major depression that occur during specific seasons. The onset and remission of depressive episodes must occur at characteristic times of the year, with symptoms consistently aligning with particular seasons.
• The seasonal pattern of depression episodes must be more prominent than any non-seasonal episodes that the individual may have experienced over their lifetime.
• The seasonal pattern of depressive episodes should be present for at least two consecutive years.
• Depressive episodes should not be better explained by other factors, such as another mental health disorder or situational stressors.

Step 2: Order Additional Testing to Uncover the Root Causes of Seasonal Depression

Once SAD has been diagnosed, additional tests can be helpful in understanding the root causes of the depression so that therapeutic interventions can be tailored to each individual's needs, optimizing health outcomes. 

Neurotransmitter Testing

Neurotransmitter testing can play a valuable role in tailoring treatment recommendations for depression by identifying specific neurotransmitter imbalances that may be contributing to the individual's symptoms. For instance, if testing reveals low serotonin levels, interventions such as supplementation with tryptophan or selective serotonin reuptake inhibitors (SSRIs) may be recommended to alleviate depressive symptoms. Conversely, low dopamine levels may prompt treatment strategies focused on increasing dopamine synthesis, such as supplementation with tyrosine and phenylalanine. (7) 

Examples of neurotransmitter profiles include:

• Comprehensive Neurotransmitter Profile - 24 hr by Doctor's Data
• Neurotransmitters by ZRT Laboratory

Comprehensive Hormonal Evaluation

Measuring the 24-hour secretion patterns of cortisol and melatonin provides insight into circadian patterns. Deviations from either hormone's normal secretion pattern indicate a disruption in the body's normal circadian rhythm, which can interfere with sleep and mood. The Sleep and Stress Panel by Ayumetrix is an excellent test option.

Micronutrient Analysis

While vitamin D deficiency is most strongly tied to SAD, more than 20 different nutrient deficiencies, including B vitamins, zinc, magnesium, and omega-3 fatty acids, have been linked to depression. 

Detecting nutrient deficiencies can be accomplished with any one of these tests: 

• Micronutrient Test by SpectraCell Laboratories
• Cellular Micronutrient Assay by Cell Science Systems
• NutrEval FMV by Genova Diagnostics

Comprehensive Stool Analysis

The gut plays a crucial role in mental health through its bidirectional communication with the brain, known as the gut-brain axis. This communication occurs via various pathways, including the nervous, immune, and endocrine systems. 

The gut microbiota, comprising trillions of microorganisms residing in the gastrointestinal tract, produce neurotransmitters and metabolites that influence brain function and mood regulation. Additionally, the gut microbiota can modulate inflammation, neurotransmitter synthesis, and the integrity of the gut barrier, all of which have implications for mental health.

A comprehensive stool analysis is a good starting point to screen for gastrointestinal imbalances that may be manifesting as mental and emotional symptoms:

• GI-MAP by Diagnostic Solutions
• GI360 by Doctor's Data
• GI Effects® Comprehensive Profile - 3 day by Genova Diagnostics

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Treatment Plan for Seasonal Depression

Clinical guidelines recommend using light therapy, antidepressants, cognitive behavior therapy (CBT), and lifestyle interventions, alone or in combination, as first-line treatment for SAD. High-quality evidence supports that these therapies reduce depression scores in patients with SAD (10). Alternate therapies can also be used adjunctively to customize treatment based on lab results, improving treatment efficacy. 

1. First-Line Interventions

Here's Why This Is Important: 

Standard of care medical guidelines recommend the use of light therapy, antidepressants, and CBT as first-line therapy. These interventions effectively treat SAD episodes and are likely to prevent recurrences in the long term. (10) 

How Do You Do This?

Light therapy uses light boxes with a light intensity of 2,500 to 10,000 lux for 30-60 minutes every morning, shortly after waking (10). One meta-analysis demonstrated that light therapy is as effective as pharmaceutical antidepressant medications. 

SSRIs, such as fluoxetine (Prozac), are first-line pharmacotherapy for SAD and have been shown to significantly improve depression scores compared to placebo in clinical trials. 

Some patients may want to avoid the use of medications. A number of evidence-based dietary supplements have demonstrated similar efficacy in research to antidepressant drugs in reducing the symptoms of mild-to-moderate depression, including:

• St. John's Wort 900 mg daily
• Lavender Oil 80-160 mg daily
• Saffron 30 mg daily

Psychotherapy, such as CBT, involves working with a trained mental health professional to explore underlying issues, challenge negative thought patterns, and develop coping strategies to gain insight into the causes of depression, learn adaptive ways of thinking and behaving, and build resilience to prevent relapse. Evidence shows that combining CBT with pharmacotherapy is significantly more effective at treating depression and preventing relapse than pharmacotherapy alone. (11) 

2. Lifestyle Interventions

Here's Why This Is Important:

Lifestyle interventions address environmental factors that impact mood and establish the foundations for optimal mental health. These interventions provide natural and accessible ways to alleviate symptoms of depression and improve overall quality of life, complementing other treatment approaches.

How Do You Do This?

Making sustainable and healthy changes to dietary and exercise habits is the best way to start forming a solid foundation for mental health. 

Growing evidence supports the connection between diet and mental health. Specifically, an anti-inflammatory diet has been shown to improve mental health outcomes. To do this: 

• Your diet should consist of whole, minimally processed foods such as fruits, vegetables, whole grains, legumes, nuts, and seeds.
• Incorporate sources of omega-3 fatty acids, such as fatty fish (salmon, mackerel, sardines), flaxseeds, chia seeds, and walnuts.
• Minimize consumption of sugary beverages, refined carbohydrates (white bread, pasta, pastries), and processed snacks.
• Eat a variety of colorful fruits and vegetables rich in antioxidants and phytonutrients.
• Add anti-inflammatory spices and herbs to your meals for added flavor and health benefits.
• Drink plenty of water throughout the day to stay hydrated.

Incorporate regular physical activity into your routine, aiming for at least 30 minutes of aerobic exercise most days of the week. Choose activities you enjoy, such as walking, jogging, dancing, or yoga, to boost mood and energy levels.

To alleviate stress and anxiety symptoms, practice stress-reduction techniques such as mindfulness meditation, deep breathing exercises, progressive muscle relaxation, or yoga. Establish a regular self-care routine that includes activities you find relaxing and enjoyable.

Stay connected with friends and family members for emotional support and social interaction, even if it means scheduling virtual or outdoor gatherings during the winter months. Fostering a social community and sense of belonging can prevent depression.

3. Correct Nutritional Deficiencies and Hormonal Imbalances

Here's Why This Is Important:

Imbalances in vitamin D, melatonin, and serotonin are the leading theories as to why SAD develops. 

How Do You Do This?

A diverse and well-balanced diet should provide sufficient vitamins, minerals, and proteins for mental health. In general, you should focus on eating plenty of foods rich in these vitamins and minerals:

• B Vitamins: whole grains, meat, fish, eggs, dairy, green leafy vegetables
• Vitamin C: citrus, tomatoes, bell peppers, broccoli, kiwi, strawberries 
• Vitamin D: salmon, sardines, swordfish, cod liver oil
• Magnesium: nuts, seeds, black beans, green vegetables
• Zinc: oysters, pumpkin seeds
• Iron: red meat, liver, dark leafy greens, tofu

Sometimes, diet alone may not be sufficient to correct deficiencies quickly. Dietary supplements that complement a healthy diet can restore nutritional levels to an optimal range. 

Remember that poor gut health may be underlying nutrient, hormonal, and neurotransmitter imbalances. A gut-healing protocol that emphasizes eating anti-inflammatory foods, restoring the gut microbiome, and using supplements to restore gut barrier function and reduce intestinal inflammation may be necessary. 

The Risks of Untreated Seasonal Depression

Without appropriate treatment, symptoms of depression associated with SAD may worsen over time, leading to increased severity and duration of depressive episodes. SAD can significantly impair social, occupational, and academic functioning, making it difficult to maintain relationships, perform well at work or school, and engage in daily activities. (25) 

Severe untreated depression, including SAD, is associated with an increased risk of suicidal thoughts and behaviors. It's essential to seek help if you or someone you know is experiencing suicidal ideation. You can call or text the 988 Suicide & Crisis Lifeline, which provides 24-hour confidential support to anyone in crisis. 

Seasonal Depression Case Study

Read about how one doctor helped a real patient with seasonal depression here:

Lisa's Natural Resolution of Seasonal Affective Disorder: A Case Study

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Key Takeaways:

• Diagnosing and treating seasonal affective disorder prevents unwanted and potentially life-threatening complications associated with untreated depression. 
• By recognizing the characteristic seasonal patterns of depressive episodes and implementing appropriate interventions, such as light therapy, psychotherapy, medication, and lifestyle changes, individuals with SAD can effectively manage their symptoms and improve their mental well-being. 
• Prompt diagnosis and treatment not only alleviate suffering but also reduce the risk of worsening symptoms, impaired functioning, and suicide. 
• Healthcare providers and individuals alike must prioritize early intervention and comprehensive management of SAD to mitigate its adverse impact and promote optimal mental health and quality of life.