Young woman with seasonal depression looking out the window on a rainy day

Seasonal Affective Disorder (SAD) – Symptoms & Causes

by | Jul 10, 2024 | Blog

Seasonal affective disorder (SAD) is a type of depression that people experience during certain seasons, particularly the winter months. It is now referred to as major depressive disorder with a seasonal pattern (MDD-SP). 

Seasonal depression tends to begin and end at the same time each year. For most people, it will start to come on in the fall and worsen during the winter months. Symptoms will often disappear during spring and summer. This is known as ‘winter depression’. Sometimes, people experience SAD during the summer months. In the case of ‘summer depression’, symptoms will appear during spring or early summer and ease during fall and winter.

Experiencing seasonal affective disorder can feel like you’re in a dark hole with no way out. You may feel hopeless and helpless, like there’s nothing you can do to make yourself feel better. But there are ways you can combat seasonal depression and improve your outlook on life. In this article, we’ll explore symptoms of SAD, what causes it, and things you can do to feel better. 

Symptoms of seasonal affective disorder

Every person will experience seasonal depression differently, but there are some common symptoms that many people experience. These include:

  • Low energy or fatigue
  • Feeling sad or down for most of the day, nearly every day
  • Feelings of hopelessness, helplessness, worthlessness, or guilt
  • Trouble concentrating or making decisions
  • Withdrawing from friends 
  • Loss of interest in activities you once enjoyed
  • Disrupted sleep patterns, i.e. oversleeping or trouble sleeping
  • Changes in appetite, weight, or both
  • Feeling irritable or agitated
  • Heaviness in limbs (arms and legs)
  • Having thoughts of death or suicide.


There are specific symptoms that are experienced with winter depression, or SAD that appears during the winter season. These include:

  • Oversleeping
  • Changes in appetite, such as craving carbohydrates
  • Fatigue or low energy
  • Weight gain. 


Summer depression, or SAD that appears during the summer months, also has unique symptoms. These include:

  • Difficulty sleeping (insomnia)
  • Lack of appetite
  • Agitation or anxiety
  • Weight loss
  • Episodes of violent behavior
  • Feeling irritable. 


If you’re experiencing any of these symptoms, it’s important to see a mental health provider. They can help you determine whether your symptoms are related to seasonal major depression or another condition. 

What causes seasonal affective disorder?

There are a few different theories on what causes seasonal depression, but the most likely explanation is that it’s caused by a combination of environmental and biological factors. Most research has focused on winter-pattern SAD, as it’s more common, and so less is known about summer-pattern SAD. 


Here’s what research suggests causes seasonal depression:

  • Changes to the biological clock (circadian rhythm): Reduced sunlight during fall and winter can change your biological clock, which regulates your mood, sleep, and hormone levels. This change in daylight length can disrupt your usual daily schedule and lead to feelings of depression.
  • Chemical imbalance in the brain: Brain chemicals (neurotransmitters), such as serotonin, may be responsible for seasonal affective disorder. Serotonin affects mood and helps contribute to feelings of happiness. Sunlight helps regulate serotonin, and so reduced sunlight during winter can drop serotonin levels in the brain and trigger depression. It’s also possible that people who experience SAD already have lower serotonin activity, making them more susceptible to depression. 
  • Vitamin D deficiency: Vitamin D helps boost serotonin levels in the brain, and sunlight is an important source of vitamin D. Lack of sunlight during the winter can lead to many people being deficient in vitamin D, which can consequently affect serotonin levels and impact your mood.
  • Changes in melatonin levels: Melatonin is a hormone that helps control the body’s natural sleep-wake cycle. Reduced sunlight during winter can cause some people to overproduce melatonin, leading to feelings of sluggishness and sleepiness during the winter months. 
  • Negative thoughts about winter: People who experience winter-onset depression often feel stress, anxiety, or negative thoughts about the colder months of the year. Researchers are unsure whether these negative thoughts contribute to seasonal depression or are a result of it. 
  • Fewer social activities: Many people will have fewer social activities during the winter months, which can lead to feelings of loneliness or isolation and contribute to depression. 

How common is seasonal depression? 

Seasonal depression is fairly common, affecting about 4-6% of the population according to the AAFP Journal. There are likely many more people beyond that number who experience a milder form of seasonal depression, known as the ‘winter blues’. 

Who is at risk of seasonal depression?

SAD is reported more often in people assigned female at birth, and it usually affects people younger than 55. You are also at higher risk of experiencing seasonal affective disorder if: 

  • You have been diagnosed with another mood disorder, such as major depressive disorder or bipolar disorder
  • You have a family history of seasonal depression or other mental health conditions, including major depression or schizophrenia
  • You live at latitude far north or south from the equator, where there is less sunlight during the winter
  • You live in a region where it’s often cloudy and overcast
  • You are low in vitamin D.

How is seasonal affective disorder (SAD) diagnosed?

If you’re experiencing any of the symptoms of seasonal depression mentioned in this article, it’s best to visit a mental health professional for a careful evaluation. Seasonal affective disorder is sometimes a part of more complex mental health conditions and an experienced professional can help you accurately identify the reason for your depression. 

When you see a mental health provider, they’ll start by asking about your symptoms and how often you experience them. You may also need to fill out a depression questionnaire with various questions about your symptoms and experiences. This will help them determine whether you have seasonal affective disorder or another mood disorder. Sometimes, a healthcare provider might request further testing to rule out other potential conditions, such as thyroid. 

Typically, to be diagnosed with seasonal affective disorder, a person needs to: 

  • Have symptoms of depression, or the more specific winter or summer-pattern SAD symptoms outlined above
  • Experience depressive episodes during specific seasons for at least two consecutive years
  • Experience depressive episodes more frequently during those specific seasons than during other times of year. 

How is seasonal affective disorder (SAD) treated? 

Now that we know what causes seasonal depression and how common it is, let’s look at different ways you can treat SAD and its symptoms. 

Light therapy

Light therapy, also known as phototherapy, involves exposure to a special type of light. This lamp is made from fluorescent light tubes covered with a plastic screen that blocks ultraviolet rays. To be effective, the intensity of the light should be 10,000 lux which is around 20 times brighter than a regular indoor light. 

How do you use light therapy?

Phototherapy involves being exposed to this light indirectly. This means you shouldn’t look directly into the light, but simply place it a few feet away from you while you go about your daily activities. Being exposed to this bright light can help regulate your body’s natural sleep-wake cycle and improve mood symptoms. 

When should you do light therapy?

In most cases, using light therapy during the morning seems to be the most effective. Some people experience insomnia when using the light later in the day. The general recommendation is to use it for 15 to 30 minutes each morning. 

How long does it take for light therapy to work?

Most people with seasonal depression who use light therapy will experience results within a couple of days. The total amount of time you use it will vary depending on your individual situation. Some people may only need light therapy for a few weeks while others may require several months of exposure in order to experience full benefits. If needed, you can continue to use light therapy for the entire winter.

Who should avoid light therapy?

Light therapy is generally safe and well-tolerated for most people. However, it may not be recommended if you: 

  • Have diabetes or a retina condition: There is a potential risk of light therapy causing damage to your retina, and so light therapy should be avoided.
  • Take certain medications: Medications like antibiotics or anti-inflammatories can make you more sensitive to light, rendering light therapy harmful. 
  • Have bipolar disorder: Light therapy can trigger hypomania or mania in some people. Let your mental health provider know if you have bipolar before beginning light therapy.

What are the side effects of light therapy?

While light therapy is generally well-tolerated, some people experience side effects such as:

  • Fatigue
  • Headaches
  • Insomnia
  • Eye strain
  • Irritability.

Antidepressant medications

There are certain antidepressant medications you can take to treat seasonal affective disorder symptoms. These are known as selective serotonin reuptake inhibitors (SSRIs) and work by regulating the level of serotonin in your brain.

Working with a medication management provider can help you find the right medication and dosage for your specific symptoms. Some SSRIs that can help relieve SAD include:

  • Fluoxetine (Prozac)
  • Escitalopram (Lexapro)
  • Sertraline (Zoloft)
  • Paroxetine (Paxil). 

Another type of antidepressant that can be used for SAD is called bupropion. This comes in the form of extended-release tablets, that when taken daily from fall to early spring, can help ease or prevent winter-onset depression. 


Although it might be difficult to engage in exercise during particularly cold or hot weather, it can go a long way in boosting mood and helping ease depression symptoms. Even just being outside for 30 minutes a day to move your body can release endorphins, which have mood-boosting properties. 

Taking a brisk walk in the sun can also help improve your mood by exposing you to vitamin D. Many people with winter-pattern SAD have vitamin D deficiency, and getting a good dose of this vitamin can help lower risk of depression and ease symptoms.

Social activities

Social activities can help fight seasonal depression by giving you an opportunity to connect with others. When you’re feeling down, it can be helpful to talk to someone who understands what you’re going through or can provide support when you need it. Participating in social activities can also help improve your mood by providing a distraction from negative thoughts. 

Some social activities that may help fight seasonal depression include:

  • Going to a support group
  • Participating in a book club
  • Volunteering
  • Attending religious services or general community events.

Diet & supplements

A healthy diet and supplements can help improve your mood by providing essential nutrients for your body. Some nutrients that can be beneficial for people with SAD include: 

  • Omega-3 fatty acids: This is a type of fatty acid found in seafood, nuts, and seeds, that has been shown to be effective in improving mood symptoms.
  • Vitamin D: This is a nutrient that’s essential for healthy bones and has been linked to a lower risk of depression. 
  • Folate: This is a water-soluble vitamin found in leafy green vegetables, legumes, and nuts. It’s also been shown to be helpful in reducing depression symptoms. 

Change your routine

People with seasonal depression may find that breaking from their normal routines can help lessen the effects of the condition. This might include taking a vacation, changing your work hours, or taking a break from any stressful obligations. 

It can feel difficult to stick to a daily routine when you’re feeling down, and taking a break can help provide some relief from that pressure. It can also be helpful to try new activities or hobbies that can help distract from negative thoughts.

Avoid alcohol

It may be tempting to reach for alcohol in times when you’re feeling down, however it can actually have the opposite effect and make depression symptoms worse

Alcohol is a depressant, which means it can slow down your brain’s activity. Drinking alcohol interrupts the production of serotonin, which is important for mood-regulation and often low in people with depression. Alcohol can also disturb sleep, which is already a problem for people with seasonal depression. 

How to prevent seasonal affective disorder (SAD)

While there’s no surefire way of preventing SAD from occurring, you can take some steps to manage it or prevent it from coming back. Some helpful preventative measures for seasonal depression include:

  • Using your light therapy: You can start using your lightbox in early fall, before you feel SAD symptoms, to help reduce their intensity. 
  • Spend time outside: Even if the sun isn’t out, it’s worth getting outside each day and exposing yourself to the daylight. This can help improve your mood.
  • Keep a healthy diet: If you find yourself craving carbohydrates, try your best to maintain a healthy diet that focuses on whole foods with vitamins and minerals. This ensures you get the nutrition and energy you need and can prevent fatigue and deficiencies.
  • Move your body: Try to get at least 30 minutes of exercise three times a week. This can release endorphins, improving your mood, while also relieving stress and anxiety which can worsen SAD symptoms. 
  • Stay social: Even when it starts getting cold out, keep making time for your friends and family. This can provide support and a pleasant distraction during the winter months and reduce feelings of loneliness and isolation.
  • Seek help: Don’t be afraid of speaking to a mental health professional early on to get support for SAD before symptoms begin to appear. They may recommend talk therapy or antidepressants to prevent SAD episodes.

Support for seasonal depression

If seasonal depression is impacting your quality of life, help is available. At BestMind Behavioral Health, we provide affordable, best-in-class behavioral and mental health treatment for people experiencing seasonal affective disorder and other mood disorders. Our providers offer medication and alternative therapies to treat seasonal depression, anxiety, bipolar disorder, and treatment-resistant depression.

Every person who comes to BestMind has their own unique needs and special circumstances. That’s why we’ve created a system that allows for total flexibility. We offer both in-person and telehealth appointments, and accept a variety of insurances, so you can get the care you need at an affordable cost. 

If you’re struggling with seasonal depression, please reach out to us at BestMind Behavioral Health. You don’t have to go through this alone – we can help!