Seasonal Depression: What It Is, How It Is Diagnosed, and How It Is Treated

Shorter days change how many people feel. Some notice they are slower to get going, sleep longer, or want more comfort food. For some people, a true depressive episode arrives in the same season, year after year, and lifts when the season changes. Psychiatry treats these as different situations. This article explains how, using the American Psychiatric Association's descriptions.

"Seasonal affective disorder" is a common name, not a separate diagnosis

Seasonal affective disorder, or SAD, is the familiar term. You may also hear seasonal depression or winter depression. The American Psychiatric Association explains that the diagnostic manual psychiatrists use, the DSM-5-TR, does not list SAD as its own disorder. It is diagnosed as major depressive disorder with a seasonal pattern.

That wording matters. "With seasonal pattern" is a specifier. A clinician first decides whether someone has a mood disorder. Then the specifier describes how the episodes behave over time. APA's published DSM-5 update also shows that the seasonal pattern specifier applies within bipolar disorders, not only major depression. For bipolar disorders, it can describe the timing of manic, hypomanic, or depressive episodes.

Winter blues, a depressive episode, and a seasonal pattern

It helps to separate three things.

Winter blues

APA notes that moments of sadness, or feeling down, are part of normal human experience. Feeling a little flat in January is not a diagnosis.

A major depressive episode

APA's depression overview explains that a diagnosis of depression requires symptoms most of the day, nearly every day, for more than two weeks, with a clear change in day-to-day functioning. Examples of that change include work or school performance, relationships, and hobbies. The symptoms APA lists include:

• sad, empty, irritable, or hopeless mood
• loss of interest or pleasure in things you used to enjoy
• a significant change in appetite or weight
• sleeping too little or too much
• low energy or increased fatigue
• restlessness, or slowed movement or speech, noticeable to others
• feeling worthless or excessively guilty
• trouble thinking, concentrating, or making decisions
• thoughts of death or suicide

A seasonal pattern

This describes depressive episodes that begin at a characteristic time of year and fully remit at a characteristic time of year. APA's DSM-5 update gives the example of depression that disappears in the spring. The specifier does not apply when the timing is better explained by seasonal stressors, such as seasonal unemployment or a school schedule. A hard semester that always starts in September is not, by itself, a seasonal mood pattern.

This is an overview, not the complete diagnostic criteria. The DSM-5-TR contains additional requirements for the seasonal pattern specifier, and a clinician applies the full criteria during an assessment.

What seasonal depression often looks like

According to APA, winter-pattern symptoms usually begin in fall or winter, when there is less daylight, and usually improve with spring. In the United States, January and February tend to be the hardest months. A summer pattern exists but is much less common.

Seasonal episodes often have a distinct profile. APA's DSM-5 update notes that depressive episodes with a seasonal pattern are often marked by loss of energy, sleeping more than usual (hypersomnia), overeating, weight gain, and carbohydrate craving. APA's patient page describes fatigue even with too much sleep. This differs from the insomnia and poor appetite many people associate with depression. Because these symptoms can look like "just being tired in winter," they are easy to dismiss.

APA reports that about 5% of US adults experience SAD. It is more common farther from the equator, in younger people, and in women. It typically starts between ages 18 and 30, though it can begin at any age. APA links it to changes in the brain's internal clock, or circadian rhythm, as daylight shortens.

Children and teens

Young people can have depression too. The AACAP guide for families explains that occasional sadness is a normal part of growing up. Sadness, irritability, or loss of enjoyment that happens day after day may signal depression. AACAP notes a depressed child may seem sad, tearful, or irritable, sleep more or less than usual, or have less energy. AACAP advises that a comprehensive assessment by a qualified professional is how depression is diagnosed.

Why bipolar disorder is part of the conversation

The seasonal pattern specifier is not limited to major depression. APA's DSM-5 update shows it also applies within bipolar disorders, where it can describe the timing of manic, hypomanic, or depressive episodes. APA describes bipolar mood episodes as distinct periods lasting days to weeks, either manic or hypomanic (abnormally happy or irritable mood) or depressive. So a winter low can sometimes be part of a broader mood pattern, and a clinician may ask about your mood history beyond the winter months.

What an assessment involves

A screening questionnaire can flag symptoms. It cannot diagnose. APA describes a diagnostic evaluation for depression as a thorough interview about your symptoms and your personal, medical, and family history, plus a physical examination to look for medical conditions that can mimic depression.

For seasonal symptoms, APA specifically notes that SAD can be misdiagnosed when hypothyroidism, hypoglycemia, infectious mononucleosis, or other viral infections are present. Proper evaluation is key.

Expect questions like:

• When did symptoms start, and when did they lift in past years?
• How have sleep, appetite, weight, and energy changed?
• How are work, school, and relationships affected?
• Were there stressors at the same time of year, like a job season or a school calendar?
• Is there a family history of depression or bipolar disorder?
• Have you had thoughts of death or suicide?

How seasonal depression is treated

APA describes several effective options, used alone or together. A clinician helps choose based on your diagnosis, history, and preferences.

Light therapy

This uses a light therapy box that gives off very bright light and filters out ultraviolet rays. APA notes most people see some improvement within one to two weeks, and treatment is usually continued through the winter. Talk with your clinician before starting light therapy.

Psychotherapy

APA notes that talk therapy, especially cognitive behavioral therapy (CBT), can effectively treat SAD. CBT focuses on recognizing unhelpful thinking patterns and changing thoughts and behaviors. AACAP lists CBT and interpersonal psychotherapy as effective for young people with depression.

Medication

APA notes that antidepressants, most commonly selective serotonin reuptake inhibitors (SSRIs), are used to treat SAD.

Daylight and daily structure

APA notes that more daylight exposure, regular exercise, healthy eating, enough sleep, and staying connected can help some people. These support treatment. They are not a replacement for it when symptoms are significant. APA also advises discussing the risks and benefits of direct sun exposure with your physician.

Timing and planning ahead

Symptoms often ease when the season changes, but APA notes treatment can help them improve sooner, especially when they are severe. Because the pattern can return, some people plan ahead with their clinician before the next fall.

When to reach out

You do not need to wait for a set number of weeks to ask for help. The two-week timeframe is part of how a diagnosis is made. It is not a rule for when you deserve care. Reach out if your mood concerns you, is getting worse, keeps coming back each fall or winter, or is making work, school, or relationships harder.

If you have thoughts of suicide or feel unsafe, do not wait. Call or text 988 or chat with the 988 Suicide & Crisis Lifeline, available 24/7, free and confidential. If you or someone else is in immediate danger, call 911 or go to the nearest emergency room.

Support at Midwest Wellness Center Associates

Our team in Chicago and Westmont offers psychotherapy and care for depression. If seasonal changes in mood are affecting your life or your child's, you can Request More Information.

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Sources (all accessed Nov 6, 2026):

• American Psychiatric Association, Seasonal Affective Disorder (SAD)
• American Psychiatric Association, What Is Depression?
• American Psychiatric Association, DSM-5 Update, February 2020 supplement
• AACAP, Depression in Children and Teens, Facts for Families No. 4 (updated October 2018)
• 988 Suicide & Crisis Lifeline (crisis resource only)