Medically ReviewedSeasonal affective disorder (SAD), also called seasonal depression, is a form of depression linked to specific times of the year, usually starting in fall or winter and improving in spring or summer. It is considered a subtype of major depression or bipolar disorder and is different from “winter blues.”
SAD is more common in areas farther from the equator due to reduced daylight exposure. In the United States, about 5 percent of adults experience SAD, with symptoms lasting nearly half the year.
The brain produces serotonin in response to different natural lighting conditions. The pineal gland then converts serotonin into melatonin, which regulates the sleep-wake cycle. Changes in the environment, genetics, changes in hormone production, and other factors can throw off the body's circadian rhythm, leading to SAD. Illustration by The Epoch Times, Shutterstock
What Are the Types of SAD?
SAD has two main types based on when symptoms occur: fall/winter and spring/summer patterns.
1. Winter-Pattern
Also called fall-onset SAD and winter depression, winter-pattern SAD is the most common form. Its symptoms typically begin in late autumn or early winter and improve in spring or summer. It’s linked to shorter days and less sunlight.2. Summer-Pattern
Also known as spring-onset SAD and summer depression, summer-pattern SAD is much less common than the first type, accounting for only 10 percent of all SAD cases. Its symptoms appear in late spring or early summer and ease during fall or winter. It may be related to excessive heat, longer daylight hours, or disrupted sleep cycles.What Are the Symptoms of SAD?
The symptoms of SAD vary by individual and throughout the year. For instance, fall-onset cases typically start out mild in the autumn and worsen as winter progresses. Furthermore, the nature and severity of the symptoms differ from person to person.
The most common symptoms of SAD include:
- Sleeping more than usual and feeling drowsy during the day
- Losing interest and enjoyment in activities once loved
- Withdrawing socially and becoming more sensitive to rejection
- Feeling irritable, anxious, or restless
- Experiencing guilt, hopelessness, or worthlessness
- Persistent fatigue or low energy
- Reduced libido
- Difficulty concentrating and thinking clearly
- Increased cravings for sweets and carbohydrates
- Weight gain
- Lethargy or irritable
- Unexplained physical aches, headaches, cramps, or digestive issues that persist despite treatment
- Suicidal thoughts or ideation
- Indecisiveness
- Irritability
- Fatigue
- Difficulty interacting with others
- Heightened sensitivity to rejection
- A heavy, “leaden” sensation in the arms or legs
- Sleeping excessively
- Increased appetite, particularly for carbohydrate-rich foods
- Weight gain
- Insomnia
- Weight loss
- Reduced appetite
- Restlessness or anxiety
- Aggressive or violent behavior
SAD symptoms do not recur annually for all who have it, with between 30 percent and 50 percent experiencing no symptoms in consecutive winters. In 40 percent of cases, depressive episodes persist beyond winter, often resulting in a diagnosis change to major depressive disorder or bipolar disorder.
Milder in symptom severity, “winter blues” occur occasionally during the colder months, causing feelings of sadness or a desire to stay home, but without significantly impairing daily functioning. People may cancel social plans and prefer solitude but still engage in normal activities such as watching TV or enjoying their hobbies.
What Causes SAD?
SAD is thought to have multiple causes, with various theories explaining its origin. In addition to environmental factors, such as changing daylight hours and geographic position, the main possible causes involve circadian rhythm and genetics. However, these theories have not been thoroughly tested.
1. Disrupted Circadian Rhythm
Circadian rhythms are the 24-hour cycles of physical, mental, and behavioral changes in an organism. While light and dark are the primary influences, factors such as food intake, stress, physical activity, social environment, and temperature also play a role in regulating these rhythms. Three major theories attempt to explain how disturbed circadian rhythms cause SAD: the phase shift hypothesis, the photoperiod hypothesis, and the retinal subsensitivity hypothesis.Phase Shift Hypothesis
SAD may arise from disrupted circadian rhythms, with winter SAD linked to a lack of sunlight and summer SAD tied to excessive sunlight. Affected individuals struggle to adjust their sleep-wake cycle to match the seasonal changes in the night-day cycle, thus leading to mood, sleep, and behavior issues.Photoperiod Hypothesis
Photoperiod is the length of daylight hours. The photoperiod hypothesis suggests that shorter daylight hours in winter may induce depression in susceptible individuals due to extended melatonin secretion. Often referred to as the “feel-good” chemical, serotonin is a neurotransmitter that regulates mood, sleep, and appetite. In the pineal gland, serotonin is converted into melatonin, a hormone that controls the sleep-wake cycle, with melatonin levels rising at night to promote sleep. While serotonin helps maintain wakefulness and a positive mood during the day, melatonin signals the body to sleep in the dark. Disruptions in serotonin levels, such as in SAD, can affect melatonin production.People with winter depression produce excess melatonin, leading to increased sleepiness and oversleeping. In contrast, individuals with summer depression may have lower melatonin levels, with long days, high temperatures, and sleep disruptions contributing to depression symptoms.
Retinal Subsensitivity Hypothesis
Light exposure directly affects mood through retinal cells sensitive to light (especially blue light), which influences the brain areas that regulate mood. The retinal subsensitivity hypothesis suggests that reduced retinal response to lower light levels in winter may disrupt circadian rhythms, thus contributing to SAD.2. Genetics
Genes linked to SAD are primarily expressed in the brain and regulate circadian rhythms. They influence gene expression timing, neurotransmitter production (such as dopamine and serotonin), and related functions. Dopamine affects blood pressure and body temperature, which vary by time of day, while serotonin is converted into melatonin, a hormone signaling sleep.Who Is at Risk of SAD?
The following factors heighten one’s risk of developing SAD:
- Sex: Similar to other types of depression, SAD is more common in women than in men.
- Age: SAD can develop during adolescence or adulthood, but adults aged between 18 and 30 years are at an increased risk of developing it. After one’s 30s, the risk lowers with age.
- Geographic location: People who live in regions far north (e.g., northern states in the United States) or south of the equator experience long winter nights.
- Depression, bipolar disorder, or other mental illnesses: SAD is more common in individuals with depression or bipolar disorder, particularly bipolar 2 disorder, which includes recurrent depressive and hypomanic episodes. People with SAD are also more likely to have other mental health conditions, such as attention-deficit/hyperactivity disorder (ADHD), eating disorders, anxiety, or panic disorder.
- Family history: SAD does not follow a clear pattern of inheritance but is more common among first-degree relatives of those affected, with about 15 percent of individuals with SAD having an affected parent or sibling. Additionally, a large portion of people with SAD have relatives with other mood or psychological disorders, such as major depressive disorder or schizophrenia. These overlaps may reflect shared genetic risk factors, although such conditions are also common in the general population, making familial occurrence potentially coincidental in some cases.
- Vitamin D deficiency: This deficiency may worsen symptoms in people with winter-pattern SAD, as vitamin D is thought to enhance serotonin activity. Since the body produces vitamin D through sunlight exposure, reduced daylight in winter can lead to lower vitamin D levels, further decreasing serotonin activity in those with SAD.
- Personality traits: People prone to anxiety may be more likely to develop SAD.
- Psychological factors: These involve the way some people process emotions and their thought patterns.
How Is SAD Diagnosed?
Early recognition of SAD and intervention are crucial, as they can significantly reduce symptoms before they fully develop.
To accurately diagnose and manage SAD, it’s important to gather a detailed medical history. SAD often occurs alongside other conditions, such as alcohol use, anxiety, or personality disorders, which can make diagnosis and treatment more complicated.
When taking a patient’s history, doctors focus on several key areas: the timing and pattern of symptoms (especially how they change with the seasons), specific symptoms experienced, how the condition affects daily life, past episodes and treatments, and any family history of similar issues.
Key areas of focus in a mental status examination for SAD include appearance and behavior, speech, mood and affect, thought process and content, perceptual disturbances (e.g., hallucinations), cognitive function, and judgment. Additionally, patients with SAD undergo a risk assessment to evaluate whether they pose any safety risks to themselves or others.
Popular screening instruments include:
- Seasonal Pattern Assessment Questionnaire (SPAQ): The SPAQ is a six-item tool that measures seasonal changes in sleep, social activity, mood, weight, appetite, and energy levels using a scale from zero (no change) to 4 (significant change). While widely used, it has been criticized for being overly broad.
- Seasonal Health Questionnaire (SHQ): Compared to SPAQ, the SHQ is considered a more reliable and valid tool for screening patients with SAD.
Diagnostic Criteria
According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR 2022), SAD is classified as a subtype of major depressive disorder and bipolar disorder, defined by a “seasonal pattern” specifier. Diagnosis requires meeting the criteria for major depressive disorder or bipolar disorder, along with demonstrating that at least one mood episode (depressive, manic, or hypomanic) follows a seasonal pattern.The criteria for the “seasonal pattern” specifier include the following:
- Temporal pattern: Major depressive episodes in major depressive disorder or mood episodes in bipolar disorder occur during a specific season.
- Seasonal remission: Symptoms show complete remission or a significant reduction in severity at a predictable time of year.
- Two-year consistency: Over the past two years, seasonal mood episodes must show a clear seasonal pattern, with no nonseasonal episodes of the same polarity during this period.
- Lifetime predominance: Mood episodes with a seasonal pattern must outnumber nonseasonal episodes across the individual’s lifetime.
What Are the Possible Complications of SAD?
Similar to other forms of depression, untreated SAD can worsen and lead to serious complications, such as:
- Impaired functioning
- Suicidal thoughts or behaviors
- Social withdrawal and isolation
- Difficulties at school or work
- Substance abuse: Some individuals may self-medicate with alcohol or drugs, leading to worsened symptoms, impaired judgment, and addiction risks.
- Relationship strain: Symptoms such as irritability and withdrawal can create tension and conflict in personal relationships.
- Physical health risks: SAD may lead to changes in appetite, sleep issues, and reduced activity, increasing the risk of obesity and cardiovascular problems.
- Worsening mental health: Untreated SAD can lead to recurrent depression or the development of other mood disorders.
What Are the Treatments for SAD?
Treatment for patients with SAD typically involves a combination of the following approaches.
1. Bright Light Therapy (BLT)
Bright light therapy is a key treatment for SAD, typically involving 30 to 60 minutes of daily exposure to 10,000-lux light in the early morning from fall to spring. The light box used in BLT is 20 times brighter than regular indoor lighting and filters out harmful UV rays.According to the Canadian Mental Health Association, roughly 60 percent to 80 percent of individuals with SAD experience significant relief from light therapy. However, those with specific eye conditions or taking certain medications (e.g., psoriasis medications, antibiotics, and antipsychotics) that increase sunlight sensitivity may need alternatives or medical supervision during treatment. The side effects of light therapy are typically mild and may include nausea, headaches, and eye strain.
2. Dawn Simulation
Dawn simulation involves a low-intensity wake-up light that gradually brightens at a set time in the morning while an individual sleeps, thus simulating a natural sunrise to help regulate the patient’s sleep-wake cycle. As per a 2015 study, dawn simulation offers the benefit of being used in a nonclinical setting and is as effective as BLT for treating winter depression. However, patients with more severe depression may experience greater improvement with BLT, which could outweigh the benefits of dawn simulation.3. Psychotherapy
Psychotherapy, particularly cognitive behavioral therapy (CBT), helps manage SAD symptoms by addressing negative thought patterns and behaviors. CBT for SAD (CBT-SAD) typically involves two weekly group sessions over six weeks, focusing on replacing season-related negative thoughts (e.g., about winter darkness or summer heat) with more positive ones. It also includes behavioral activation, helping individuals schedule enjoyable activities to combat the loss of interest common in winter or summer.When compared directly with BLT, both treatments were equally effective in improving SAD symptoms, although light therapy showed slightly faster improvements in some areas. However, the benefits of CBT seemed to persist longer over time.
4. Antidepressants
Antidepressants can effectively treat SAD, either alone or in combination with therapy. They work by altering brain chemicals involved in mood and stress. It typically takes four to eight weeks for antidepressants to show results, with improvements in sleep, appetite, and concentration often occurring before mood improves. It’s important to give one type of medication time to work and to be open to trying different options to find the most effective one.The following are two kinds of antidepressants used in treating SAD:
- Selective serotonin reuptake inhibitors (SSRIs): SSRIs (e.g., fluoxetine and sertraline) are commonly used to treat SAD due to their ability to address disturbances in serotonin activity, which is associated with depression. SSRIs can significantly improve mood and are considered effective primary treatments for SAD.
- Bupropion: The U.S. Food and Drug Administration (FDA) has approved an extended-release form of bupropion, an antidepressant that can help prevent the recurrence of seasonal depressive episodes when taken daily from fall to early spring.
5. Vitamin D
Exposure to sunlight is a natural method of intervention. People with SAD can spend more time outdoors during the day or install skylights if feasible.When sun exposure is not possible, vitamin D supplements may help improve symptoms of fall-onset SAD, as many people with this condition have a deficiency. However, study outcomes on its effectiveness have been mixed, with some suggesting it is as effective as light therapy and others find no significant impact.
6. Brain Intervention Therapies
These may include the following:- Electroconvulsive therapy (ECT): During ECT, a controlled electric current is used to induce a generalized cerebral seizure in a patient who is under intravenous sedation or general anesthesia. ECT is a controversial treatment for mental illness, but it is considered safe and effective for severe depression when other treatments, such as medication and talk therapy, don’t work.
- Repetitive transcranial magnetic stimulation (rTMS): Transcranial magnetic stimulation uses short magnetic pulses to stimulate nerve cells in the brain to alter the function of brain circuits involved in mood regulation. rTMS can be effective for patients with depression who do not respond to initial antidepressant treatment.
- Magnetic seizure therapy (MST): Magnetic seizure therapy involves inducing a seizure by applying magnetic stimulation to the brain. It has been found to be equally effective as ECT in significantly reducing symptoms of major depression.
7. Self-Help
The following self-help tips may be useful in coping with SAD:- Seek help: If you suspect you’re depressed, consult a health care provider as soon as possible.
- Set achievable goals: Don’t overwhelm yourself. Break large tasks into smaller steps, prioritize, and tackle them at your own pace.
- Socialize and confide: Spending time with others and opening up can be more helpful than isolating yourself.
- Engage in activities you enjoy: Find things that lift your spirits. Doing something kind for someone else can also improve your mood.
- Exercise regularly: Regular physical activity has been proven to alleviate depression symptoms and increase serotonin levels, thus helping to counteract the effects of SAD.
- Be patient with your progress: Understand that improving your mood will take time and won’t happen overnight.
- Follow a healthy diet: A nutritious, balanced diet, especially one rich in complex carbohydrates found in fruit, vegetables, and whole grains, can improve your mental health by positively affecting mood and energy levels. Foods high in omega-3 fatty acids, like fatty fish, flaxseeds, and kidney beans, may also have a positive effect on depression, research outcomes are mixed.
- Avoid alcohol and drugs: These substances can worsen depression and interfere with your recovery.
- Avoid prolonged screen time: This is especially important around bedtime.
- Postpone major decisions: Avoid making significant life changes while depressed. Consult trusted individuals for guidance.
- Focus on the positives: Be patient with yourself and try to shift your focus to positive thoughts as your depression improves with treatment.
- Allow support from loved ones: Let your family and friends offer their help during this time.
- Schedule routine checkups: Arrange consistent checkup appointments to track symptom severity, assess treatment effectiveness, and monitor any potential medication side effects, ensuring comprehensive care throughout the seasonal cycle.
How Does Mindset Affect SAD?
Cultivating a positive mindset is important, as it helps individuals use effective coping strategies against SAD such as performing outdoor activities, socializing, and practicing mindfulness.
A mindset focused on solutions encourages proactive steps such as undergoing light therapy. Furthermore, believing in the effectiveness of treatments improves adherence and outcomes.
What Are the Natural Approaches to SAD?
The natural methods outlined below may help treat SAD and depression in general. However, before attempting any of them, please consult your health care provider.
1. Herbal Medicinals and Dietary Supplements
- Saffron (Crocus sativus): Saffron has been used in traditional medicine for centuries to address various health issues. It has been known to help with digestion, relaxation, relieving spasms, clearing mucus, improving appetite, and boosting mood and energy. A 2020 meta-analysis of 12 studies found saffron to be as effective as synthetic antidepressants in improving depressive symptoms, thus making it a potential natural alternative for treating mild to moderate depression. However, larger, longer-term studies are still needed to confirm these findings.
- St. John’s wort (Hypericum perforatum): St. John’s wort is named after John the Baptist because it blooms near his feast day in late June. Traditionally, the herb has been used to treat conditions such as kidney and lung issues, insomnia, and depression. A 2023 meta-analysis of 14 clinical trials found that St. John’s wort was effective in reducing symptoms in depressed patients and had fewer risks and side effects than standard medications such as SSRIs. Another 2017 meta-analysis of 27 clinical trials found the herb as effective and safe as SSRIs in treating patients with mild-to-moderate depression.
- Lavender (Lavandula angustifolia): Lavender has been used throughout history to treat insomnia, anxiety, and depression, along with other ailments. A 2021 meta-analysis of 17 clinical trials found lavender to possess excellent antidepressant effects. The lavender products used in these studies include lavender capsules, tea, essential oil, and cream.
- Dehydroepiandrosterone (DHEA): DHEA is a hormone produced by the body. A 2018 meta-analysis found DHEA to be a potential alternative to depression medications. A 2005 study also found DHEA to be an effective treatment for midlife-onset major and minor depression.
2. Aromatherapy
Aromatherapy involves the use of essential oils for therapeutic purposes. In a 2021 meta-analysis of 38 studies, lavender aromatherapy has been shown to significantly reduce anxiety and depression, with longer sessions providing stronger effects. However, its impact on physical health measures is small and inconsistent.3. Hypnotherapy
Hypnosis, also known as hypnotherapy, is a technique that induces a trance-like state of deep relaxation to address psychological or emotional disorders.A 2024 scoping review of 14 studies found that hypnotherapy had often been combined with psychotherapy, and in most studies, it had effectively reduced depression symptoms and might surpass antidepressants in boosting health and vitality. Another 2019 meta-analysis showed that hypnotherapy is highly effective in reducing depression symptoms and is comparable to other psychological interventions.
4. Meditation
Meditation helps manage stress and anxiety, major triggers of depression, by training the brain to maintain focus and resist negative thoughts. It also alters brain regions linked to depression and prepares the mind for handling stress.A 2016 meta-analysis of 18 studies found that meditation therapies might benefit patients with clinical depressive disorders during the acute and subacute treatment phases. In a 2021 study, inpatients with major depression experienced significant reductions in depressive symptoms when using mantra meditation as an adjunctive treatment. Mantra meditation involves silently repeating a spiritual sound, word, or phrase with focused attention on the mantra.
Another 2024 review of 26 randomized controlled trials found that mindfulness-based meditation significantly reduced depressive symptoms in people who practiced during the COVID-19 pandemic.
5. Yoga
While all types of exercise improve mood by reducing stress hormones, increasing endorphins, and boosting brain oxygen, yoga may offer extra benefits by raising levels of gamma-aminobutyric acid (GABA), a brain chemical linked to improved mood and reduced anxiety. A 2023 meta-analysis of 34 studies found yoga capable of alleviating depressive symptoms and anxiety in patients with major depressive disorder.How Can I Prevent SAD?
As SAD usually follows a predictable pattern, preventative measures may help alleviate symptoms. Prevention strategies for SAD include lifestyle changes and targeted interventions, such as the following:
- Increasing exposure to natural sunlight
- Adopting a healthy diet
- Engaging in regular physical activity
- Ensuring adequate sleep
- Taking daily walks during daylight
- Optimizing living spaces for sunlight exposure
- Practicing meditation and other stress-management techniques
- Taking vacations in sunnier climates
- Implementing light therapy in the fall and winter, even before symptoms appear
- Employing psychological interventions such as CBT
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