Seasonal Affective Disorder: Symptoms & Causes

Written by:Kate Rosenblatt, MA, LPC, LMHC

Published On: February 9, 2022

Medically reviewed by: Dr. Karmen Smith, LCSW, DD

Reviewed On: February 9, 2022

Updated On: April 19, 2023

Overview

Also called seasonal depression, seasonal affective disorder (SAD) is a mental health condition marked by feelings of depression and meaninglessness that occur at roughly the same time each year. SAD generally occurs during the winter months, although a rare form of seasonal depression known as summer depression or reverse SAD can be experienced during the warmer summer season.

Seasonal depression symptoms can be debilitating and overwhelming, but this highly treatable condition doesn’t have to rule your life. It’s important to seek help so you can learn to manage winter SAD and get through the season experiencing the joy you deserve from life.

Read on to learn more about what seasonal affective disorder is and what its causes, risk factors, diagnosis prerequisites, and treatment options are.

Symptoms of Seasonal Affective Disorder

There are multiple possible seasonal depression symptoms. The symptoms differ for those who suffer from SAD in the summer months relative to those who experience it during the winter.

Seasonal depression in fall or winter

As noted earlier, most people experience seasonal depression symptoms in the colder winter months. Associated symptoms are similar to those of general depression and can include:

Feeling hopeless & exhausted
Desire to be left alone
Increased appetite
Low energy levels
Irritability
Difficulty focusing
Suicidal thoughts
Weight gain
Fatigue

Many people with SAD feel down nearly every day. They may lose interest in activities they once enjoyed, replacing them with increased eating and sleeping.

Seasonal depression in the summer or spring

Those who experience SAD during the summer months may have different symptoms, including:

Reduced appetite
Weight loss
Trouble sleeping
Agitation
Restlessness

However, the underlying feelings of worthlessness, guilt, and hopelessness are also often still present in summertime.

Causes of Seasonal Depression

While research hasn’t been able to truly define a precise cause of SAD, some prevalent theories are being tested. Researchers believe that people with SAD may produce less serotonin, a brain chemical partially responsible for our mood.

Those with seasonal depression also seem to produce more melatonin, a hormone that’s responsible for regulating sleep. Their bodies typically produce too little vitamin D, which has direct and indirect roles in sleep regulation.

Another reason could also be your circadian rhythm. Because of shorter daylight hours, your body’s circadian rhythm may be disrupted which can cause depressive symptoms to develop.

Diagnosing Seasonal Depression

Doctors look for the following symptoms to diagnose seasonal affective disorder:

Depression or mania that repetitively begins and ends at the same times each year
Symptoms that self-resolve, disappearing during “normal” (warmer) seasons
Symptoms that have repeated for at least 2 consecutive years

Answering the question: what is seasonal depression can be a bit tricky. It can be difficult for a doctor to diagnose because it shares symptoms with various other disorders marked by depression and/or mania — including bipolar disorder, chronic fatigue syndrome, hypoglycemia (low blood sugar), certain viral illnesses, and an underactive thyroid, to name a few.

It’s for this reason that seeking help is so imperative if you think you’re experiencing SAD symptoms. A doctor can rule out any other medical conditions, so you can begin effective, helpful treatment to help you get through the season.

Seasonal Depression Risk Factors

Certain factors have been linked to an increased chance of developing seasonal affective disorder, including gender, age, where you live, and having a family history of depression.

Sex

Age

Women are about 4 times more likely to have SAD than men.

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Frequently Asked Questions

How common is seasonal depression?

SAD is quite common. In fact, research shows that an estimated 5% of people in the US may struggle with SAD every year. For most people, the seasonal pattern of SAD starts in late autumn or early winter and continues into late spring or early summer.

If you’re struggling with symptoms of SAD, know you’re not alone; there’s an estimated 10M Americans struggling with these symptoms each year. If you’re feeling symptoms that are similar to depression around the winter months in particular, it can be helpful to track your daily depressive symptoms, rate them on a 0-10 scale of intensity to note any changes, and reach out to a therapist to talk through how you’ve been feeling and what treatment options might feel best for you.

As many as 25 million more Americans may experience a lesser form of SAD known as “the winter blues” or winter depression.