Seasonal Affective Disorder

Key Takeaways

• SAD is a seasonal mood disorder that can manifest as a form of depression or bipolar. The disorder can occur in winter or summer, with winter being more common.

• Symptoms include sadness, a loss of interest in activities previously enjoyed, fatigue, overeating, and sleeping excessively.

• Bright light therapy is the primary treatment, with complementary recommendations including psychotherapy, antidepressants, and vitamin D supplements.

Understanding Seasonal Affective Disorder

Seasonal affective disorder goes beyond the commonplace “winter blues” and is a mental health condition far more serious than transient sadness. The disorder can disrupt emotional stability, physical health, and brain function significantly - particularly during months with less daylight. However, in rare cases, seasonal affective disorder can manifest during the summer months.^[1][2]

Classified as an additional set of criteria for either bipolar disorder or major depressive disorder, seasonal affective disorder varies in terms of the depressive and bipolar symptoms associated with it. In depressed individuals, the disorder appears seasonally as a loss of interest in activities once enjoyed, a melancholy mood, and low energy levels.^[1][3]

When it comes to bipolar individuals with the condition, seasonal affective disorder manifests during either summer or winter in the form of depression, mania, or hypomania. Unlike the usual forms of bipolar and depression, when the triggering season changes (e.g., from winter to spring or summer), symptoms disappear completely.^[1][3]

In addition to the typical symptoms of depression or bipolar disorder, individuals with seasonal affective disorder may also struggle with excessive sleep (hypersomnia), an increased appetite, and unmanageable cravings for carbohydrates. Fortunately, several evidence-based treatments have been shown to reduce symptoms significantly.^[1]

Prevalence of SAD

The prevalence of seasonal affective disorder varies globally, tending to rise in regions further from the equator where there are shorter days during winter. As a result, many researchers believe there may be a connection between the onset of the condition and reduced exposure to natural light.^[1]

As the seasons change, the body’s internal clock (referred to as the circadian rhythm) can become misaligned, which can interfere with an individual’s daily functioning and routine. It is estimated that between 1% and 10% of the population may have the condition, depending on how far they live from the equator.^[1][2]

Seasonal affective disorder has been found to be more common in women than in men, with women being affected up to 9 times more often. Younger individuals (particularly women) are more likely to be affected, with most people having their first episode at around the age of 30, and the prevalence between men and women tending to decrease with age.^[2][3]

SAD in Young People

The difference in how seasonal affective disorder impacts individuals appears to be linked to young adults, who are at a stage of peak hormone activity. Compared to older adults, young people tend to be more sensitive to subtle environmental changes, such as shifts in sunlight exposure.^[1]

That said, research surrounding seasonal affective disorder in young people is still in its infancy, meaning that further studies are needed to shed light on the link. At this stage, while scientists have theorized that there is a connection, there is not much evidence to support the exact causes or mechanisms of seasonal affective disorder.

Does SAD Only Occur During Winter?

While rare, some individuals experience seasonal affective disorder during the spring or summer months instead of fall or winter. However, fall-onset depression has been studied far more extensively than spring-onset depression, with limited research available on summertime manifestations of the disorder.^[1][2][4]

While winter depression is thought to be triggered by reduced sunlight, summer depression stems from other unknown factors. Summer seasonal affective disorder is not only rarer - but also tends to resemble typical, non-seasonal depression, often involving symptoms like insomnia, reduced appetite, weight loss, restlessness, and anxiety.^[3][5]

The progression of seasonal affective disorder can differ from person to person, but even in those who are affected during winter, symptoms may continue into the summer months. However, although people with the disorder may experience depression at other times of the year, seasonal episodes must significantly outnumber non-seasonal ones in order to be diagnosed.^[1][6]

Symptoms of SAD

Seasonal affective disorder is not a standalone diagnosis in the DSM-5 but is classified as a “specifier” (specific form) of both major depressive disorder and bipolar disorder. A specifier is a term used in mental health diagnoses to identify certain features of a disorder. For example, in the case of seasonal affective disorder, the "with seasonal pattern" specifier indicates that symptoms occur only during certain seasons.

In other words, seasonal affective disorder presents with symptoms of either depressive or bipolar episodes seasonally - although not all individuals with depression or bipolar disorder exhibit the “with seasonal pattern” specifier. This means that to meet the criteria for seasonal affective disorder, an individual must also have symptoms of bipolar or depression.^[1]

Seasonal Affective Disorder Symptoms (Episodes of Depression)

According to the Diagnostic and Statistical Manual for Mental Disorders, Fifth Edition (DSM-5), to meet the criteria for a major depressive episode, a person must experience at least five or more of the following symptoms nearly every day, for most of the day. At least one of the symptoms must be a depressed mood or loss of interest or pleasure in activities:^[7]

• Sadness, emptiness, or hopelessness (or irritability in children/teens)

• Loss of interest or enjoyment in most activities

• Noticeable weight or appetite changes not related to intentional diet changes

• Trouble sleeping or sleeping too much

• Restlessness or slowed movements noticeable to others

• Low energy or constant fatigue

• Feelings of worthlessness or inappropriate guilt

• Trouble concentrating or making decisions

• Thoughts of death or suicide, with or without a plan

In terms of symptoms, seasonal affective disorder has a lot in common with the features of regular depression listed above. However, unlike typical depression, people with winter-onset seasonal affective disorder tend to sleep more, eat more (due to carbohydrate cravings), and gain weight, similar to what is referred to as atypical depression.^[3]

On the other hand, individuals with summer-onset seasonal affective disorder exhibit symptoms of insomnia, anxiety, agitation, reduced appetite, and weight loss. These symptoms tend to manifest in addition to other depressive criteria listed above. When it comes to seasonal bipolar disorder, symptoms present differently.

Seasonal Affective Disorder Symptoms (Episodes of Bipolar I and II)

To diagnose seasonal affective disorder that manifests as bipolar I or II, a person must first meet the standard criteria for bipolar disorder. In addition, they must have experienced at least one bipolar mood episode (whether in the form of depression, mania, or hypomania) that consistently occurs during a specific season.^[1][8]

Mania

A manic episode is a period lasting at least one week (or any duration if hospitalization is needed), where a person experiences an unusually high, irritable, or overly enthusiastic mood, along with a noticeable boost in energy or activity levels. These changes must be present most of the day, nearly every day.^[7]

To qualify as mania, the symptoms must be severe enough to disrupt work, social interactions, or daily functioning, may require hospitalization, or involve psychotic symptoms like delusions (false beliefs). During this time, the person shows at least three of the following signs - or four if the mood is mainly irritable:^[7]

• Feeling unusually powerful, important, or overly confident

• Sleeping far less without feeling tired

• Talking excessively or feeling unable to stop talking

• Racing thoughts or quickly jumping between ideas

• Being easily distracted by things around them

• Taking on too many tasks or acting overly restless

• Engaging in risky behavior (e.g., overspending, reckless sex, or poor business choices)

Hypomania

A hypomanic episode is similar to mania but less severe and must last at least 4 days in a row, with elevated or irritable mood and increased energy most of the day. It involves the same symptoms as mania and is noticeable to others, but hypomania:^[7]

• Does not cause major problems at work or in relationships

• Does not require hospitalization

• Does not include psychosis

When a person with bipolar experiences a depressive episode, the symptoms present in the same way as major depression disorder, particularly atypical depression. Individuals with the seasonal form of bipolar tend to have increased rates of both obesity and suicidal thoughts or behaviors.^[1][7]

Additional “With Seasonal Pattern” Specifier

In addition to exhibiting symptoms of either bipolar or depression, to be diagnosed with seasonal affective disorder, mood episodes must follow a clear seasonal pattern, appearing during a specific time of year, for a minimum of two years. These symptoms usually fully resolve at a predictable seasonal point, such as remission in the spring or summer.^[1]

Causes of Seasonal Affective Disorder

Although the exact cause of seasonal affective disorder is not known, research suggests it likely results from a combination of biological, environmental, and genetic factors. Additionally, several theories involving sunlight exposure have been proposed to explain why most individuals develop the condition during the fall and winter months.^[1]

Reduced Sunlight Exposure

Seasonal affective disorder most commonly begins in seasons when daylight hours are shorter, like fall and winter. The lack of sunlight during these seasons is believed to disrupt the body’s natural rhythms and affect brain chemicals (including dopamine) involved in mood regulation.^[1]

Circadian Rhythm Disruption

One of the leading theories in the cause of SAD is that seasonal changes throw off the circadian rhythm, which helps to regulate sleep, mood, and hormone production. Two main models explain this:^[1]

• Photoperiod Hypothesis: Shorter daylight hours cause extended melatonin production, which may lead to depressive symptoms.

• Phase Shift Hypothesis: Misalignment between a person’s sleep-wake cycle and their internal clock can trigger seasonal affective disorder.

Melatonin Imbalance

Another theory for the cause of seasonal affective disorder is that melatonin (a hormone that regulates sleep) is affected by darkness. During winter, increased melatonin production may disrupt sleep patterns and mood regulation in people with the disorder.^[1]

Serotonin and Neurotransmitter Changes

Seasonal affective disorder has been linked to the dysregulation of serotonin (a neurotransmitter involved in mood stability). Other brain chemicals linked to mood and mental health, including dopamine, norepinephrine, and glutamate may also be involved, although the exact mechanisms remain unclear.^[1]

Additionally, studies have shown that lowering tryptophan levels can trigger depressive symptoms in people with seasonal affective disorder. Tryptophan is an amino acid, which is a building block of protein. It is needed to create proteins in the body and is also used to produce serotonin.^[1]

Light Sensitivity and Retinal Response

Light exposure can directly impact a person’s mood because certain cells in the eye, especially those sensitive to blue light, play a role in regulating mood. Additionally, the retinal subsensitivity theory suggests that the eye’s reduced response to lower light levels in winter may disrupt the body's natural rhythm and contribute to seasonal affective disorder.^[1]

Genetic and Family History

A family history of mood disorders such as depression or bipolar disorder increases the risk of developing SAD. Furthermore, the seasonal subtype of bipolar disorder affects 15% to 25% of individuals with the condition, with depressive episodes in winter or fall being the most common.^[1]

Some studies suggest possible links between seasonal affective disorder and genetic differences related to the dopamine and serotonin pathways (these chemicals play a key role in mood regulation, with imbalances potentially contributing to mood disorders), though results are still inconclusive.^[1]

Seasonal Gene Expression

Recent findings show that certain genes are more active during winter or summer. These shifts in gene activity may influence how the brain responds to seasonal changes, possibly contributing to seasonal affective disorder.^[1]

Diagnosing SAD

Diagnosing seasonal affective disorder requires a thorough assessment, including a complete patient history and a mental health check-up, following set guidelines. The DSM-5 (considered the diagnostic Bible of mental health) classifies the condition as a type of major depressive disorder or bipolar disorder, along with a "seasonal pattern" set of criteria.^[1]

This means that although the disorder follows a clear seasonal pattern, it is not listed as a standalone disorder in the DSM-5. Instead, it is considered a "specifier" (additional criteria) for either major depressive disorder or bipolar disorder. There is ongoing debate surrounding how the condition should be classified in the DSM-5, with experts calling for further research.^[1]

Seasonal affective disorder can be challenging to diagnose because its symptoms are similar to other types of depression or bipolar disorder. As a result, it may take time for medical professionals to notice a recurring pattern of symptoms. Seasonal affective disorder is typically diagnosed if:^[8]

• Symptoms of depression or bipolar occur at the same time each year for at least two years

• The depressive, manic, or hypomanic episodes are followed by periods of stability

Misdiagnosis

While seasonal changes in mood and behavior have been recognized since ancient times, classifying these as a psychiatric disorder is still a subject of controversy. In addition to the DSM-5 listing seasonal affective disorder as a specifier of depression or bipolar, the 11th Revision of the International Classification of Diseases (ICD-11) classifies "seasonal depressive disorder" under the category of "recurrent depressive disorder."^[3][9]

This means that diagnostic criteria for the condition remain unclear and are hotly debated. Furthermore, the intensity of symptoms in people with the disorder can vary, with seasonal mood changes ranging from normal fluctuations to severe symptoms that affect a person’s ability to function. Many individuals with severe recurrent depression or bipolar disorder experience periods of low mood in winter and mild high mood (hypomania) in spring or summer.^[3]

Depending on where a person falls on the symptom severity spectrum, they may have full-blown seasonal affective disorder or a milder version known as subsyndromal seasonal affective disorder (or the winter blues). Individuals with the winter blues experience seasonal mood changes, but their symptoms are not severe enough to affect functionality.^[3]

Additionally, mental health professionals face the challenge of distinguishing between mood disturbances caused by events that frequently occur during a certain season, such as winter or summer unemployment, and a disorder linked directly to the season itself. Another factor to consider is that the condition can be mistaken for hypothyroidism, viral infections, or other conditions.^[2][6]

Seasonal Affective Disorder Treatments

Managing seasonal affective disorder requires a holistic approach to reduce symptoms and enhance overall well-being. Treatment typically involves a combination of bright light therapy (which is considered to be the primary treatment), psychotherapy, antidepressants, and vitamin D supplements.^[1]

Bright Light Therapy (BLT)

Dr. Norman E. Rosenthal (an American psychiatrist, New York Times bestselling author, and seasonal affective disorder coach) was the lead researcher in identifying the disorder and a pioneer in developing bright light therapy (BLT) as a treatment. This type of therapy entails sitting directly in front of a special light box that emits an extremely bright light while filtering out harmful UV rays. It has been found to bring about significant improvements in mood symptoms.^[1][2][11]

The treatment typically requires a minimum exposure of 20-30 minutes per day, usually administered upon waking on winter mornings, throughout the season. BLT is generally not used as a preventative measure, but symptom improvement is often observed within one to three weeks of starting treatment. However, bright light therapy can only reduce depressive symptoms, and there is no evidence to support its efficacy in treating mania.^[1][2]

BLT is usually continued until symptoms naturally fade in the spring or summer, meaning that the treatment only offers temporary effects. Overall, Bright light therapy is considered safe, with only mild and short-term side effects like headaches or eye strain. However, people with existing eye problems (or who are at a higher risk of eye problems) should have their eyes checked by a specialist before starting treatment.^[1]

Cognitive Behavioral Therapy for Seasonal Affective Disorder

Recent research has revealed that psychotherapy, especially cognitive-behavioral therapy (CBT), can help people with seasonal affective disorder manage their symptoms by identifying and challenging unhelpful thoughts and behaviors that contribute to low mood. This form of therapy teaches individuals to manage their thoughts and emotions independently over time.^[1][2]

A version of CBT tailored for seasonal affective disorder (known as CBT-SAD) focuses on shifting negative thoughts related to the seasons and encouraging healthy, mood-enhancing behaviors. One study found that CBT-SAD works just as well as light therapy and has longer-lasting effects over two years.^[1]

Medication

Selective serotonin reuptake inhibitors (SSRIs) are a common class of antidepressants often used to treat seasonal affective disorder. The medication can be taken on its own or used alongside bright light therapy. However, bupropion XL is the only medication specifically approved for preventing seasonal depression.^[1]

A major review conducted in 2019 showed that individuals with depression or bipolar disorder who begin taking bupropion in the months before symptoms typically begin can lower the risk of depression returning during the winter months. However, a meta-analysis from 2016 states that bupropion does not lower the risk of an individual with bipolar transitioning from depression into mania.^[1][12]

Vitamin D Supplementation

Unfortunately, people living in areas above 33 degrees north or below 30 degrees south of the equator cannot produce vitamin D from sunlight during the winter months. Data has confirmed that many individuals with winter-pattern seasonal affective disorder have low vitamin D levels, suggesting that taking vitamin D supplements might help manage depressive symptoms.^[1][13]

Supplementation is seen as a complementary treatment that should be used alongside BLT, therapy, and antidepressants. This is because although vitamin D supplements show promise, studies have shown mixed results, and it is not yet clear whether vitamin D alone is effective for treating seasonal affective disorder.^[1][13]

Living with Seasonal Affective Disorder

The winter form of seasonal affective disorder is frequently compared to hibernation. Those affected tend to feel fatigued, sleep more, crave carbohydrates, and gain weight. Social withdrawal, difficulty concentrating, and a sense of heaviness in the limbs are also common. Atypical depression shares similar symptoms but is not tied to the seasons.^[6]

While there is a summertime version of seasonal affective disorder, it affects far fewer individuals. Individuals with this form of the disorder experience disturbances in sleep patterns, a loss of appetite and weight, increased irritability, and anxiety or agitation. When left untreated, symptoms of seasonal affective disorder may continue to disrupt functionality seasonally.^[14]

The condition (regardless of which season causes its onset) can impact a person’s ability to work, care for themselves effectively, maintain relationships, and may even lead to substance abuse, eating disorders, or suicide. Fortunately, a well-rounded treatment approach combined with self-care techniques, provides hope in significantly improving symptoms.^[14]

Seasonal Affective Disorder Self-Care

Winter-onset seasonal affective disorder can affect mood and energy levels as sunlight decreases, but self-care strategies may help ease symptoms. Research suggests that spending time outdoors, increasing indoor lighting, and incorporating daily movement (like morning walks) can be especially effective.

Dr. Norman Rosenthal, a seasonal affective disorder expert, recommends practices including mindfulness, yoga, and a nutrient-rich diet to support emotional well-being during the darker months. Additionally, Dr. Rosenthal has written a book on beating the disorder and offers individual coaching for individuals with the condition.

Increased Sunlight and Indoor Lighting

Studies suggest that getting more sunlight can help alleviate symptoms of seasonal affective disorder in some people. This could include spending time outdoors or setting up the home or office to ensure close proximity to a window during the day. However, UV light exposure from the sun can raise the risk of skin cancer, so it is important to wear sunscreen (even indoors).^[2]

In an older study, Swiss researchers tested whether a morning walk or sitting in front of a lightbox was more effective for relieving seasonal affective disorder symptoms. The results showed that the walkers experienced a greater mood improvement than those using the light box, suggesting physical activity could be beneficial, especially for milder cases of the disorder.^[6]

Some research suggests that light exposure at different times of day may also be helpful. Dr Norman Rosenthal (who discovered seasonal affective disorder and pioneered BLT) mentioned that some people have found relief from seasonal affective disorder using strategies like adding more indoor lighting or even planning trips to sunny places before winter sets in.^[6]

Lifestyle Changes Recommended By Dr. Rosenthal

Dr. Rosenthal promotes self-care by exploring ways to reduce the debilitating symptoms of seasonal affective disorder. In his research he has found that practices such as Transcendental Meditation (TM), mindfulness, walking, yoga, and any exercise enjoyed by different individuals helped manage symptoms.^[13]

Rosenthal also recommends a diet rich in vegetables, proteins, unprocessed foods, and complex carbohydrates. On his website, he advocates using Botox for depression and provides insight into other methods he has researched. You can reach out to Dr. Rosenthal for one-on-one coaching or read his book titled “Defeating SAD” (seasonal affective disorder) here.^[13]

Realistically, these habits will take time to build, so adopting a gradual approach with a focus on progress over perfection can support the long-term improvement of your mental health. For example, you can begin by setting aside 5 minutes every other day to meditate, 20 minutes every other day for exercise, and making small changes to your diet by slowly swapping out unhealthy foods for more nutrient-dense options.

Final Thoughts

Seasonal Affective Disorder (SAD) is a serious form of depression or bipolar disorder that manifests during specific seasons, most commonly during winter, although at times during the summer months. It can disrupt functionality and emotional stability when symptoms of depression or bipolar disorder emerge seasonally.

Fortunately, there are effective treatments that can help. Bright light therapy is the primary treatment, supplemented by cognitive behavioral therapy, antidepressants, and vitamin D. With the right treatments and self-care strategies, it is possible to reduce symptoms and break free of the debilitating bonds of this mental health condition.