Seasonal Affective Disorder – Definition, Causes, Symptoms, Diagnosis, and Treatment

SAD affects people who do not have any previously diagnosed mental problems, and they feel well during most of the year, but they tend to feel depressed or experience symptoms of depression throughout one particular season, usually winter each year. Although the term “winter blues” is often used when referring to this disorder, SAD is more than that, and it can even occur during the summer months.

Have you ever experienced mood changes as the weather or seasons change? A lot of people feel down when the weather is bad for days, especially when the autumn comes, so could it be that there is the actual scientifically explained reason behind it? People were sensitive to weather changes for ages, and the earliest records of it go back to ancient Roman times, Hippocrates was the first one who wrote about it around 400 BC, and he claimed that a lot of different diseases were connected to the change of seasons. But since then, a lot of time had passed before the American Psychiatric Association recognized this disorder in the late 90s. It has been estimated that today, this condition affects from 4% to 6% of the population.

Meteoropathy is also considered a disease, type of weather-related pain, but it refers to a shorter period of time, and isolated pain in particular body parts, on the other side, seasonal affective disorder refers to the condition which lasts much longer, for months even, and it is attached mostly to winter and autumn season. 

If you have been down and grumpy all winter, it could be because of SAD, so stay tuned to find out more about the symptoms and other useful things.

Seasonal Affective Disorder Facts

SAD affects people who do not have any previously diagnosed mental problems, and they feel well during most of the year, but they tend to feel depressed or experience symptoms of depression throughout one particular season, usually winter each year. Although the term “winter blues” is often used when referring to this disorder, SAD is more than that, and it can even occur during the summer months. 

Even though a lot of experts were skeptical, this is now a recognizable and not so rare condition whose official status was changed and redefined from just a mood disorder to a more specific one by adding the “with seasonal pattern” suffix, which defines it more closely. 

Ten million Americans are affected by it, and approximately another 10 to 20 percent of the US population has a milder form of SAD. Interestingly, this is a condition that strikes women four times more often than men. When it comes to age, people who are between 18 and 30 years old are most liable to it. 

Many tend to neglect or not to take these symptoms seriously, but some people experience symptoms so severe that they hinder their daily functioning and lower the quality of their lives, and even 6% of them requires hospitalization. Although people with SAD usually do not have any other health problems, a lot of them has some close relative with a diagnosed psychiatric disorder, in most cases (55%) that is severe depression, but alcohol abuse is also frequent. 

Winter depression or SAD is pretty common among people who live in the Nordic countries, the first records of it go back to the 6th century when a Goth scholar named Jordanes described the people of Scandinavia in his Getica. In the US, the first proposition for an official diagnosis came at the end of the 20th century, when a psychiatrist and scientist Norman Rosenthal moved to New York from sunny South Africa. He first noticed the changes in its mood, and started experimenting with the exposure to artificial light, and noticed the improvement, which made him a pioneer in this field.


Like with many other disorders, the exact cause remains unknown, despite continuous ongoing research and effort. There are some theories, but they are not wide enough to reach to the root of the problem, but then again, it could be that many different things are capable of triggering this condition. We always expect from medicine and science to give us exact and concrete causes, or answers, but when it comes to conditions such as this one, expecting one precise and unique answer could be illusory.

According to one theory, SAD occurs due to the increased production of melatonin in our body during winter days. Melatonin is a hormone in charge of our sleep-wake cycle, and it is produced in the brain’s pineal gland. As the night falls, the production of melatonin rises, reaching its peak in the middle of the night, while in the morning with the sunrise, its level goes down. Since the dark surroundings can stimulate the production of melatonin and prepare our mind and body for sleep, a lot of scientists noticed the natural connection with shorter and darker days during the winter and blamed them for winter blues and lethargy.

The same thing is with another hormone called serotonin, which is a brain chemical, a sudden drop of it affects our mood significantly; hence, scientists believe that it can be connected to SAD. Less exposure to sunlight can lower the level of serotonin and trigger depression, but it also reduces the production of vitamin D, which also plays a crucial role in the activity of serotonin. In a lot of cases, lack of vitamin D is clinically connected to signs of depression.

Animals who hibernate represent the extreme example of this condition, and their activity is completely diminished during the winter months due to the lack of sunlight, food, and change of surroundings. There are species who do not hibernate, but they go through some changes during the winter in order to survive and accommodate better.


In the vast majority of cases, symptoms will start showing during the late autumn or beginning of the winter, and they will naturally go away with spring. But, although it is much less common, the reverse case is also possible, meaning that some people experience SAD during the summer months. With the wake of spring, their symptoms rise and become more severe during the summer, in the autumn they should be okay again. Regardless if you are a summer or winter type, the symptoms of SAD should appear at the same time each year. 

Some of the most common signs of SAD include:

  • Feeling depressed almost all the time, each day
  • Low life energy
  • Lack of interest in the things you use to enjoy
  • Appetite changes
  • Issues with establishing a sleep routine
  • Struggling to concentrate
  • Feeling of hopelessness, worthlessness, guilt, etc.
  • Thinking about death and suicide

Since the symptoms of summer and winter SAD are specific and different, we decided to share both lists separately; however, both types can also experience some of the common symptoms of depression, for example, the feeling of guilt, helplessness, loss of interest, etc. From the below-listed symptoms, you will notice that some signs are opposite, and go from one extreme to another, which shows how we all are prone to the things we cannot control, such as seasons.

Winter SAD Symptoms:

  • Oversleeping
  • Low energy and a constant feeling of tiredness
  • Cravings for high-carb food and a gain of weight

Summer SAD Symptoms:

  • Problems with falling or staying asleep, in most cases insomnia
  • Lack of appetite and loss of weight
  • Anxiety or agitation

How to Diagnose SAD?

Due to the high number of similar mental health disorders, sometimes it can be challenging to diagnose SAD because it has a lot of the same symptoms as some other types of depression, but it is also a lot of times misdiagnosed as mononucleosis, hypoglycemia, or hypothyroidism.

The process of setting a diagnose includes several evaluations and tests, and the most common combination of them consists of:

  • Physical exam. The very first step in diagnosing SAD is a physical exam, followed by some thorough questions about the patient’s health since in a lot of cases depression is a manifestation of some other, underlying mental health problem.
  • Laboratory. All kinds of lab tests come in option, from the initial blood test to the thyroid function one, if the doctor considers that it is necessary. 
  • DSM 5. DSM stands for Diagnostic and Statistical Manual of Mental Disorders, in which the criteria for SAD are descriptive, and in a lot of cases, doctors will reach for this guide in order to be sure they are setting the right diagnosis.
  • Psychological questionnaire. To detect any signs of depression doctors will ask a series of questions about your mental health, feelings, thoughts, to try to find any possible symptoms of depression, and even give you to fill a questionnaire, which will help them determine whether or not it is SAD.


Treating this disorder is not easy, and there are several ways in which you can alleviate the symptoms, so be prepared that you might not find the solution in your first attempt. If waiting for spring seems too long and unbearable, try considering some of the most recommended treatments, which include vitamin D supplements, light therapy, counseling, and antidepressants

Since the decreased exposure to sunlight has been recognized as one of the main factors for SAD, light therapy became pretty popular and used in the purpose of reducing the symptoms of winter depression. The treatment implies regular exposure to artificial light during the morning hours, to mimic the effects of natural, outdoor light. Usually, the person needs to sit in front of a lightbox or to wear a light visor each day from 30 to 60 minutes during the fall and winter season. The exact duration of the therapy varies from one person to another, but if you notice the improvements in terms of energy and other symptoms, you should continue with it until the springtime arrives, and then gradually stop using it, if you stop your therapy too early, the symptoms can return.

Side effects of light therapy are not often discussed since its benefits are much more significant, but we would like to mention some of them here briefly. Patients claimed to have fatigue, headaches, eyestrain, or irritability; hence this form of treatment may not be suitable for patients who are diagnosed with bipolar disorder, or for those who have very sensitive skin and eyes. 

If you do not notice any improvement after a few days of practicing light therapy, then you should try with some medications or CBT behavioral therapy, individual or even in combination with light therapy. People with SAD often experience insomnia and its symptoms so CBT therapy can be pretty useful for them too. The therapist will work with patients in order to help them to be able to recognize some things and patterns which are preventing them from falling asleep so that they can change them and develop more healthier habits which will induce sleep instead of postponing it. 

Besides this, there are some behavioral changes that everyone can do with the power of will, try spending more time outside, walking, jogging, or even exercising which will raise the energy level, and clear up your mind. When indoors, you can also increase the amount of daylight in your home by opening the shades and removing curtains as much as possible, so that your home is bright and sunbathed. One study was researching how the exposure to sunlight effects on sleep of people who work in offices, the results showed that people who were working near the windows had a better sleep due to the higher exposure to daylight.

On the other hand, people who are dealing with summer SAD will probably need to do the reverse thing, buy some blackout curtains and limit their exposure to sunlight. For them, it is highly recommended to wear sunglasses when outside, and to turn off or stop using all electronic gadgets at least one hour before the desired bedtime. 

If you are into traveling, SAD can be the perfect excuse to go on an extended holiday and spend more time in the conditions you prefer, which can be particularly tempting during the cold winter days.

Besides these, it is essential to do some basic self-care precautions measures such as:

  • Take notes of your mood and energy level on a daily basis
  • Try taking the most of available daily sunlight, and exposing yourself to it
  • Make in advance a plan of joyful activities for the upcoming season
  • Try approaching the winter season with a positive attitude
  • Start practicing some physical activities
  • Once you start feeling the symptoms, seek help immediately, do not wait for them to aggravate

SAD and Sleep

SAD can be the cause why some people developed other sleep problems, or why their existing ones became even worse, and since sleep issues are one of the first signs of depression, it is not a surprise that they go along with SAD. 

People dealing with SAD are usually one of the people who divide into two major groups known as night owls and early birds, meaning that they either sleep for more than 9 hours, or less than 6, and none of those options are not considered to be healthy.

Most people with seasonal affective disorder develops hypersomnia or insomnia, but hypersomnia is more dominant as it strikes around 80% of people with this disorder. Another reason why people with SAD are struggling with the amount of sleep they get is that they tend to spend the majority of their time in bed, but they are not sleeping effectively for the most of time. They think that they are getting enough sleep and rest, but that is only an illusion, which later leads to misleading estimations and diagnosis. 

Since Nordic countries are particularly affected by this disorder, one study focused on people in Finland and the sleep problems that were common among people with SAD, in the chart below are their conclusions.

Sleep problems People with SAD who are affected General population affected by this issue
Insomnia 25% 7.6%
Nightmares  15% 2.4%
Diagnosed with depression in the last 12 months 30.4% 4.1%
Use of antidepressants over the last month 24.3% 3.6%
Use of hypnotics over the previous month 26.3% 7.6%


SAD Risk Factors

Interestingly, in a lot of disorders, there is no difference among sexes, and usually, the older we get, the more we are prone to various symptoms and diseases. But, seasonal affective disorder strikes women more often than men, and the younger population is more liable to it than seniors, which is more an exception than a rule. 

Although we do not know what causes it, there are some, generally speaking, common risk factors, which may indicate if a person has predispositions for SAD or not.

  • Family medical history. Although it has not been proved that SAD can be transferred genetically, we are familiar with the cases in which a person suffering from SAD has relatives who struggle with other types of depression.
  • Distance from the equator. We cannot choose where to be born; hence, people who were “unlucky” enough to be born or to live too north or south from the equator have higher chances for developing SAD. The number of people living remotely from the equator, and dealing with SAD should not be neglected since it shows how geographic location impacts people’s overall health. In such areas, during the summer months, the days are incredibly long, and during the winter the amount of sunlight on a daily level is not enough and can cause health-related problems.
  • Already having depression or bipolar disorder. People who are diagnosed with some similar mood disorders can experience an aggravation of their symptoms during the problematic seasons.

Possible Complications

Symptoms of SAD should not be neglected, and even when they go away with the change of seasons, they will come back next year at the same time. Hence, if it is not treated, SAD can progress over time and even trigger some other conditions and problems.

  • Problems at work or in school. Moodiness can cause problems if you are out of focus, alert, or you are not interested in participating in your daily obligations at work. Since younger adults are the major risk group, their scores at university could be jeopardized.
  • Social withdrawal. People with depression tend to act like introverts; they refuse social contact, and always have an excuse for not showing up. However, social isolation is not the solution, the best is to inform your close people and coworkers about what is going on, and they will show more understanding of your condition.
  • Substance abuse. A lot of people try to lift their mood with different substances, which inevitably leads to addiction. The thrill they can provide comes with a time limit, and as soon as it expires, the depression will hit back even harder. That is how many people get addicted to these substances, and start using them even after the season changes.
  • Eating disorder or anxiety. Anxiety and depression often go hand in hand, but an eating disorder is not lacking behind a lot. Depressive people often search for comfort in food and overeating, since it is one of the rare things that can provide them comfort and satisfaction. 
  • Suicidal behavior and thoughts. Unfortunately, this is also possible, and it happens sometimes. Depression is a dangerous condition, but since the term is so overused these days, we tend to forget how serious its consequences can be.


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