Seasonal Mental Health

Seasonal Affective Disorder: Signs, Seasons, and When to Get Help

By Dr. Stacey Forbes, DNP, APRN, PMHNP-BC

Plenty of people feel slower and flatter when the days get short, and brighter when longer daylight returns. For some, that seasonal shift is more than a mood: it changes how they sleep, eat, think, and get through the day, and it comes back on roughly the same schedule each year. That is the pattern clinicians call seasonal affective disorder, and it is worth understanding before the darker months arrive rather than halfway through them.

Two seasonal patterns, not one

The National Institute of Mental Health (NIMH) describes SAD as a type of depression marked by a recurrent seasonal pattern, with symptoms lasting about four to five months of the year. The familiar version is winter-pattern SAD, sometimes called winter depression: symptoms begin in the late fall or early winter and lift during the spring and summer.

Less often, the pattern runs the other way. In summer-pattern SAD, depressive symptoms arrive in the spring and summer months. That form matters for patients in hot-climate states, and our guide to summer seasonal depression in Arizona looks at it in more detail.

Signs to watch for

SAD includes the symptoms of depression, and not everyone has all of them. NIMH lists, among others:

• A persistent sad, anxious, or “empty” mood most of the day, nearly every day, for at least two weeks
• Feelings of hopelessness, irritability, guilt, or worthlessness
• Loss of interest or pleasure in activities you usually enjoy
• Low energy, fatigue, or feeling slowed down
• Trouble concentrating, remembering, or making decisions
• Changes in sleep or appetite, or unplanned weight changes
• Thoughts of death or suicide

Each seasonal form also has signs of its own. With the winter pattern, NIMH describes oversleeping, overeating with a particular craving for carbohydrates, and social withdrawal, the feeling of wanting to “hibernate.” With the summer pattern, the list reverses in places: trouble sleeping, poor appetite with weight loss, restlessness and agitation, and anxiety.

Not the same as the holiday blues

NIMH draws a clear line here. Sadness or anxiety brought on by holiday pressure, family visits, or the year-end rush is not SAD, even when it happens in December. The depression in SAD is tied to changes in daylight, not to the calendar or the events on it.

That distinction is useful in practice, because the two call for different conversations. If what you are feeling tracks your workload and your obligations more than the light, our article on telling burnout apart from depression is a better starting point. It is also possible to have both, which is one reason a proper evaluation is worth more than a self-diagnosis.

How SAD is diagnosed

There is no single test for SAD. A clinician listens to the history, often alongside a questionnaire, and looks for a specific shape over time. According to NIMH, a diagnosis requires:

• Symptoms of depression, or the more specific symptoms of winter- or summer-pattern SAD
• Depressive episodes that occur during a specific season for at least two consecutive years (though not everyone with SAD has symptoms every year)
• Episodes in that season that are more frequent than depressive episodes at other times of the year

This is why timing affects an evaluation. Someone seen in July may describe themselves as fine; the same person seen in January may describe a long depression. A careful history covers the whole year, so the pattern shows up whichever month the appointment falls in.

Who is more likely to develop it

NIMH notes that SAD usually begins in young adulthood and occurs much more often in women than in men. Because the winter pattern is the more common one, SAD is more common farther north, where winter days are shortest. NIMH gives the example that people in Alaska or New England are more likely to develop SAD than people in Texas or Florida.

That does not mean it cannot happen in the South: the pattern is about each person’s response to the change in light, and it shows up wherever people live. For Alaska patients, where the daylight swing is the widest in the country, our guide to seasonal affective disorder in Alaska goes further.

SAD is also more common in people who already live with depression or bipolar disorder, especially bipolar II, and people with SAD often have another condition as well, such as ADHD, an eating disorder, or an anxiety or panic disorder. It sometimes runs in families. All of that is part of why a seasonal pattern should be evaluated rather than assumed.

What researchers think is happening

NIMH is clear that the causes are still being studied, and that most of the research so far concerns the winter pattern. The leading explanations involve two chemical messengers that help keep the body’s daily rhythm in step with day length:

• Serotonin, which helps regulate mood. Studies indicate that people with SAD, especially the winter pattern, have reduced serotonin activity, and shorter days may contribute to that.
• Melatonin, which helps maintain the sleep–wake cycle. People with winter-pattern SAD may produce too much of it, which can increase sleepiness and oversleeping.
• Vitamin D, which is believed to promote serotonin activity. With less daylight on the skin in winter, people with SAD may have lower vitamin D levels. Our article on vitamin D, B12, and mood covers why nutrient levels are worth checking.

Treatment options NIMH describes

According to NIMH, treatments for SAD fall into four main categories, which can be used alone or in combination:

• Light therapy, a mainstay for winter-pattern SAD since the 1980s. Some people, including those with certain eye conditions or taking medications that increase sensitivity to light, may need an alternative or medical supervision.
• Psychotherapy, including a version of cognitive behavioral therapy adapted for SAD.
• Antidepressant medication. Antidepressants usually take four to eight weeks to work, and it can take more than one try to find the right one.
• Vitamin D. Studies of vitamin D as a SAD treatment have produced mixed results, and it can interact with some medications.

Light therapy and vitamin D are treatments for the winter pattern; psychotherapy and antidepressants are used for depression more broadly, including both seasonal forms. NIMH notes there are no treatments specific to summer-pattern SAD. Every option has potential benefits and risks, and your clinician decides with you what fits your history, your other medications, and your season.

Thinking ahead of the season

Because SAD tends to arrive on a predictable schedule, NIMH notes that people with a history of it might benefit from starting treatment before the fall (for the winter pattern) or the spring (for the summer pattern). It also says plainly that few studies have looked at whether SAD can be prevented. The practical takeaway is modest but useful: if you recognize the pattern in yourself, a conversation in late summer or early fall about timing is a reasonable thing to ask for.

How Willow & Stone approaches seasonal mood changes

Dr. Stacey Forbes, DNP, PMHNP-BC, sees patients by secure telehealth across Texas, New Mexico, Florida, Alaska, Arizona, and Colorado. An evaluation for a seasonal pattern looks at the whole year, and at what else might be moving with the season: sleep, stress, nutrition, and lab work, alongside medication where it is appropriate. For a fuller picture of how depression is assessed and treated here, see depression treatment, or read what to expect at a first appointment.

If you are noticing the pattern this year, you can request a consultation and mention it on the form.

Common Questions

Sources & Further Reading

• National Institute of Mental Health: Seasonal Affective Disorder (NIH Pub. No. 23-MH-8138, revised 2023)
• 988 Suicide & Crisis Lifeline