This is why there are so many holidays in the fall and winter months. For many, these light-hearted celebrations serve as a symbol of hope, something to look forward to when the dark days threaten to ward off seasonal depression.
Changes in timing, shorter days, and inclement weather force people to stay indoors, with seasonal depression affecting about 5% of adults annually and can last up to 40% of the year.1 Interestingly, it is 4 times more common in women than in men.2 also known as seasonal affective disorder (SAD), this recurrent major depressive disorder has a pattern of seasonal emergence and remission.
SAD is thought to be mainly caused by a lack of sunlight. More than 50% of the human population lives in the northern temperate zone between the Tropic of Cancer and the Arctic region to the north. As a result, SAD tends to peak from December to February, often coinciding with that time of year when shorter days mean less sun.
Although the purpose of the holidays is to bring us closer to friends and family, it is also a very stressful time for many people. Taking on too many commitments, family interactions, travel, and disrupted schedules can pile on the stress and make SAD symptoms worse.
Part of the challenge with SAD is its seasonality, which can alert people if they are not usually depressed. By teaching patients how to identify and address SAD, clinicians can give patients a valuable gift.
What is SAD?
SAD was first identified in 1984 by Norman Rosenthal, MD, along with other collaborators. Upon moving from his home in South Africa to the United States, Rosenthal noticed that he felt less productive and more lethargic during the winter months. Later research found that the longer people lived from the equator, the higher the rate of SAD. For example, in Florida, only 1.5% of people studied experienced SAD, while in New Hampshire it affected closer to 10%.2
Symptoms of SAD usually include persistent low mood and a lack (or perceived lack) of energy. People experiencing seasonal depression may feel more irritable than usual, cry easily or frequently, experience lethargy or fatigue, have a tendency to withdraw or become displaced socially, and Difficulty concentrating may be experienced. Affected people also sleep more than usual, experience a craving for sugars and carbohydrates, report being less active, and may gain weight.
Winter depression is the most common form of SAD, with symptoms emerging in the fall and persisting through the winter months. Its mild form is known as the “winter blues”. Less common is summer depression, which can occur in the spring and summer months. Symptoms during this time can include insomnia, loss of appetite and weight loss, and increased psychomotor activity, often resulting in agitation, restlessness, or anxiety.
In either form, cases can be severe and cause significant loss of function. Like all types of depressive disorders, suicidal thoughts can occur.
A lack of sunlight is the main cause of SAD, but there are other causes as well. A series of cloudy days, mostly indoors, and syncope with time hiccups are some of the conditions that can lead to an exacerbation of SAD.
How SAD Affects the Body
The exact cause of SAD has not been confirmed, but scientific research points to several causal factors.3
Low serotonin activity in the brain is thought to be a cause of SAD. Less sunlight leads to higher levels of the serotonin transporter protein, which can lead to a decrease in serotonin activity in the brain. In the summer months, sunlight naturally keeps levels of these proteins low.3
A lack of sunlight can also induce the overproduction of melatonin, a hormone produced by the pineal gland that controls sleep-wake.3 Decreased sunlight exposure can increase melatonin levels, which can lead to increased sleepiness and lethargy.
These disruptions in serotonin and melatonin levels can impair a person’s circadian rhythm. People with seasonal depression have more difficulty adjusting their internal clocks to seasonal changes in day length, and this can affect their sleep, mood, and behavior.
Vitamin D levels are also affected by light. Vitamin D is believed to affect serotonin levels, and deficiency is related to clinically significant depressive symptoms.3 More precisely a hormone, vitamin D is found in some foods and is also produced by the skin when exposed to sunlight.
People living in northern and southern latitudes far from the equator are at higher risk of developing SAD. In northern countries, 2% to 9% of people experience SAD, with 15% to 20% of people experiencing mild “winter blues”.4 Actual prevalence may be higher due to possible under-diagnosis or under-reporting.
SAD is much more common in women, possibly related to changes in estrogen levels. 5 It also appears more frequently in people who have a family history of depression as well as young people. The onset of seasonal depression occurs between the ages of 18 and 30.6 People engaged in shift work, such as health care workers or law enforcement agents, may be at particularly high risk.
However, the prevalence of SAD is not without its critics. A 2008 study reported that residents of northern Norway go without sun for 2 months during the winter, but do not “suddenly complain” about depression during this time.7 Another study in 2016 examined US data from a cross-sectional survey by the Centers for Disease Control and Prevention.8 The authors said they could not find any significant increase in depression rates that could be attributed to a particular season.8 Despite this criticism, it is important to identify cases of SAD to help people navigate the darkness of the fall and winter months.
SAD. how to treat
SAD is classified in both the ICD-10 and the DSM-5. To be diagnosed, a person must have experienced depression during a specific time each year for at least 2 years. Once SAD is diagnosed, there are several promising treatments to help reverse its effects.
Medicine. Antidepressants are a promising and viable treatment option for moderate to severe cases of seasonal depression.3 Although there are concerns about the side effects of these drugs, there are several new alternatives available that have shown promise. Additionally, there are other non-drug options available, such as neuromodulation, which are effective and may be better tolerated.
Psychotherapy and counseling. Psychotherapy can go a long way in reducing the distress and harm caused by the symptoms of SAD. In cases of mild depression, it may be effective on its own or in combination with medications to treat moderate to severe depression. Most of the existing research evidence supports the use of cognitive behavioral therapy.
Other modalities of psychotherapy, including mindfulness-based stress reduction, positive psychotherapy, interpersonal psychotherapy, and brief problem-focused psychotherapy, can also be highly effective. These can empower a person to effectively manage or overcome unhelpful thoughts and feelings. It can help them find successful ways to relax, preserve their ability to function, anticipate and prepare for potential emotional triggers, and what may seem like a long, dark winter. can see the light at the end of it. Interest in complimentary modalities is growing again, including psychedelic psychotherapy, also inviting more research and attention.
light therapy. Light therapy attempts to reverse the effects of reduced daylight hours by exposing a person to artificial full-spectrum light. Light boxes are readily available, often without a prescription, and are usually recommended for use during the early morning hours.3 It is similar in composition to natural sunlight, but with ultraviolet light filtered out. Medical supervision is suggested to ensure proper light intensity, as well as distance, duration, frequency and timing. This will help avoid any unwanted effects, such as headache, eye strain, and in rare cases, mania and suicidal thoughts. Light therapy is not recommended for people who take certain medications that may cause them to experience unusual sensitivity to light.
Vitamin D supplements. Preliminary clinical studies suggest that people with seasonal depression have insufficient (mild or borderline low levels) or deficient (quite low levels) vitamin D levels, which is usually due to low intake through diet, lifestyle changes, and lifestyle changes. Issues are caused by a combination of less sunlight exposure or availability during the winter/fall months or for those working night shifts. Researchers have suggested that daily supplementation with moderate to high-dose vitamin D may prevent symptoms of seasonal depression or improve ongoing symptoms.3 Although rare, there is a small risk of developing adverse effects or toxicity with very large doses of vitamin D, so physicians should work closely with patients and their primary care providers.
Lifestyle changes. There are many things people can do themselves to reduce the effects of SAD. Finding ways to reduce stress, increase physical activity, and spend time outside can help increase energy levels. Eating a diet high in protein with complex carbohydrates and vegetables and avoiding fatty foods or simple carbs may also be beneficial. Traveling to sunny places has also been linked to helping with mood.
other options. Complementary and alternative medicine options have gained popularity in recent decades due to increased awareness, research evidence, and a shift toward a more holistic approach to health care. Nutraceuticals, dietary and herbal supplements, mindfulness and meditation practices, yoga, acupuncture, and traditional practices of Ayurvedic, Unani, or Chinese medicine may be useful.
Although the concrete causes of SAD are still elusive, SAD is a clinical condition that affects millions of people each year.
Several mechanisms may play a role in its emergence, with the most notable being the reduction of light exposure during the fall and winter months. Symptoms may vary, but they share similarities with other types of depression.
Timely detection and treatment can be of great help; Lifestyle modulation and adjustments can go a long way. Because of the nature of the condition and the risk of being underdiagnosed or treated, mental health practitioners should be on the lookout for SAD when assessing referred patients.
Dr. Singh is a psychiatrist and regional medical director for MindPath Health.
1. Trafanstedt MK, Mehta S, Lobello SG. Major depression with seasonal variation: is it a valid construct? Clin Psychological Science, 2016;4(5):825-834.
2. Rosenthal NE. What is Seasonal Affective Disorder? Accessed December 22, 2021.
3. Melrose S. Seasonal affective disorder: an overview of assessment and treatment approaches. Depress Race Treat. 2015; 2015: 178564.
4. Rosen LN, Targum SD, Terman M, et al. Prevalence of seasonal affective disorder at four latitudes. psychiatric research, 1990;31(2):131-144.
5. Parthenon T. Estrogen may modulate photoperiodic adjustment in seasonal affective disorder. med hypothesis, 1995;45(1):35-36.
6. Seasonal affective disorder. American Psychiatric Association. October 2020. Accessed December 22, 2021.
7.Hansen V, Skre I, Lund E. What is this thing called “SAD”? Criticism of the concept of seasonal affective disorder. Epidemiol Psychiatric Society. 2008;17(2):120-127.
8. Turner VS. The study found that “seasonal affective disorder” does not exist. scientific American. March 15, 2016. Accessed December 22, 2021.
9. Hansen BT, Sonderskov KM, Heijmann I, et al. Daylight saving time transition and incidence rates of unipolar depressive episodes. Epidemiology. 2017;28(3):346-353.
10. Daylight Saving Time 2021: When does the time change? Almanac. November 4, 2021. Accessed December 22, 2021.
Suggestions for further reading
National Center for Complementary and Integrative Health. 6 things to know about complementary health approaches to seasonal affective disorder. Accessed January 10, 2022.