Hello Darkness, My Old Friend

Navigating Seasonal Affective Disorder (S.A.D.)

Today's newsletter was authored by Dr. Sarah Scheinman, our resident neurobiologist. It aligns with an Unbiased Science Podcast episode on seasonal affective disorder, where we welcomed special guest Dr. Nicole Lippman-Barile (@feedyourmental). You can find the episode on all major podcast platforms and YouTube.

[Note: Jess is currently at the JIFSAN-CFS3 Advisory Council Annual Symposium, presenting on risk communication and the relationship between scientific evidence and public perception. She'll share insights and key takeaways upon her return.]

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Well, folks. It’s that time of year again. Winter is coming, and that means one thing: daylight savings. Unfortunately for many of us, the changing of the seasons (and our clocks!) comes with more than just a shift in schedule. Seasonal Affective Disorder (SAD) is a distinct form of depression that usually begins in the late fall or early winter when daylight hours are shorter, and can affect the way a person feels, thinks and behaves. Symptoms often start with fatigue and low energy, and can involve sadness, lethargy, and apathy that can last up to 4-5 months out of the year. Other symptoms that are specific for winter-pattern SAD include oversleeping (hypersomnia), overeating (sometimes leading to weight gain), and social withdrawal, or feeling like “hibernating.”

Prevalence of SAD

SAD impacts a significant portion of the population during the darker months, with approximately 5% of US adults experiencing symptoms (though this is likely an underestimate).

The condition shows notable demographic patterns:

• Women are four times more likely than men to experience SAD

• Younger adults face higher risk compared to older populations

• Geographic location plays a significant role: about 1.4% of residents in Florida experience SAD, compared to 9.7% in New Hampshire (based on 2019 data)

• Individuals with existing mental health conditions show increased susceptibility:

  • 10-20% of those with major depressive disorder

  • Approximately 25% of those with bipolar disorder

A brief history of SAD

SAD was first formally recognized as a distinct form of depression in the early 1980s, though people have long observed that mood and energy levels can fluctuate with the seasons. The history of SAD's recognition and research involves several key milestones:

1. Early Observations: Historical accounts suggest that people have experienced seasonal mood changes for centuries. There are references to "winter blues" or low moods during colder, darker months. However, it wasn’t until the 20th century that these observations began to be explored systematically.

2. 1980s - Formal Recognition: The term "Seasonal Affective Disorder" was coined by Dr. Norman Rosenthal, a psychiatrist and researcher at the National Institute of Mental Health (NIMH). In 1984, Rosenthal and his colleagues published a groundbreaking paper in the journal Archives of General Psychiatry detailing their research on people whose depression worsened in the winter months and improved in the summer. Their work was inspired by Rosenthal’s own experiences after moving from South Africa to the northeastern United States, where he noticed significant mood changes during winter. This paper marked the formal recognition of SAD as a subtype of major depression.

3. Development of Light Therapy: One of the most significant advancements in SAD research was the development of light therapy in the 1980s. Researchers found that exposing patients to bright artificial light for a period of time each day could significantly alleviate SAD symptoms. This was based on the theory that the shorter daylight hours in winter contribute to mood disorders by disrupting circadian rhythms and reducing serotonin production.

4. Diagnostic Criteria and DSM Inclusion: In 1987, SAD was included as a "specifier" in the Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R), allowing it to be diagnosed as a seasonal pattern of major depressive disorder. Later editions of the DSM continued to recognize SAD, reinforcing its legitimacy as a clinical diagnosis.

5. Continued Research and Expanded Understanding: Over the following decades, research expanded to understand the biological mechanisms behind SAD. Studies have focused on the roles of melatonin, serotonin, and the circadian rhythm. Research has also explored the genetic and environmental factors that might predispose someone to developing SAD. For example, those who live at higher latitudes (where daylight hours are shorter in winter) or who have a family history of depression are more susceptible.

6. Beyond Winter Depression: Although SAD is most commonly associated with winter, it has been observed that some people experience symptoms of depression during the summer, known as "summer SAD." This variant of the disorder is less common but is recognized by researchers and clinicians.

Today, SAD is widely accepted as a specific mood disorder with clear seasonal patterns, and treatments like light therapy, cognitive behavioral therapy (CBT), and antidepressant medications are commonly used to manage the condition.

The Biology of SAD

SAD has strong ties to our biology, particularly through the concept of circadian rhythm, our body’s internal 24-hour clock. These rhythms respond to changes in light in our environment and play a crucial role in regulating cycles of alertness and sleepiness. At the center of this system is the suprachiasmatic nucleus (SCN), a tiny cluster of neurons in the hypothalamus that primarily processes light signals. It is connected to other brain regions involved in hormone production, such as the pineal gland, which produces melatonin (the sleep hormone), and the raphe nucleus, responsible for serotonin production, a key neurotransmitter that regulates mood.

During a typical 24-hour period, our brain emits rhythmic signaling in response to light/dark cycles, utilizing chemical messengers like cortisol and cytokines. Sunlight is the most powerful stimulus for regulating circadian rhythm because the SCN summates the amount of light we get in a 24-hour period. When days are shorter and sunlight is limited, especially during the winter months, this disruption can interfere with your body’s ability to maintain a balanced mood.

Reduced daylight can also lead to a drop in serotonin and norepinephrine levels, leading to feelings of sadness and fatigue, and an increase in the production of melatonin, which can increase sleepiness and lead to hypersomnia (oversleeping). This intricate system highlights how disruptions in our circadian rhythms, particularly, during seasonal changes, can contribute to the onset of SAD, affecting mood and overall well-being.

How is SAD treated?

Treating seasonal affective disorder often involves a combination of approaches to help alleviate symptoms and improve mood. One of the most effective treatments is light therapy, which involves exposure to a specially designed light box that mimics natural sunlight, helping to regulate circadian rhythms and boost serotonin levels. Several clinical trials have demonstrated the effectiveness of this approach for regulating the body’s internal clock during periods of limited daylight hours. The recommended duration for light therapy is around 20-30 minutes each morning, and many users report reductions in feelings of depression, fatigue, and irritability following consistent treatment.

Psychotherapy, particularly cognitive behavioral therapy (CBT), can also be beneficial for addressing negative thought patterns and providing coping strategies for managing seasonal mood changes such as incorporating exercise and sleep hygiene practices into daily routines. In some cases, antidepressant medications such as Selective Serotonin Reuptake Inhibitors (SSRIs) may be prescribed to help balance neurotransmitter levels in the brain, offering additional relief from depressive symptoms. Ultimately, by combining a number of different therapeutic approaches, individuals with SAD can find a tailored approach that support their mental health throughout the changing seasons.

While shorter days and diminished sunlight can certainly affect our mood, there are numerous ways to soften the impact of SAD on our quality of life. Taking advantage of sunny days – whether it’s a brisk walk outside or a cup of coffee on the porch – can help regulate our circadian rhythms and lift our spirits. Bringing light into your home, whether through light therapy, or simply keeping curtains open during the day, can also make a difference. Staying connected to family and friends is another vital strategy, as social interactions can alleviate feelings of isolation.

Don’t underestimate the power of a balanced diet and regular exercise; both can help stabilize your mood and ground your circadian rhythms, even when natural light is scarce. And above all else, it is important to practice self-compassion during the winter season. Cultivating a supportive mindset encourages resiliency, making it easier to cope more effectively with challenges and navigate negative emotions. Please be kind to yourself!

Stay curious,

Unbiased Science