Seasonal depression (SAD)
When the days get shorter and your mood sinks with them, it’s not just in your head. Seasonal depression is real, common and very treatable.
By the numbers
How common seasonal depression is, and what the research shows.
How common
What helps
What is seasonal depression?
A type of depression that comes back at the same time each year.
Seasonal affective disorder (SAD) is a type of depression that follows a repeating seasonal pattern. Symptoms usually last about four to five months a year. The winter pattern is most common: it starts in late fall or early winter and eases in spring and summer.
A less common summer pattern brings low mood in spring and summer instead. SAD is tied to changes in daylight, not to the calendar, so holiday stress on its own is not SAD.
Read more
SAD is a type of depression. It can affect how you feel, think and manage daily life, and it can be treated.
Read more
People who get the right diagnosis and combination of treatments can find relief. SAD can come back each year, but steps taken early can prevent or lessen symptoms.
Winter pattern and summer pattern
The two patterns can feel almost opposite.
Both patterns can bring the usual signs of depression: a sad or empty mood, losing interest in things, tiredness, trouble concentrating and feeling hopeless or guilty. Each pattern also has its own typical changes.
Read more
It can look like
- Anxiety
- Poor appetite and weight loss
- Restlessness and agitation
- Trouble sleeping
- Violent or aggressive behaviour
Read more
It can look like
- Craving carbs and overeating, sometimes with weight gain
- Oversleeping and still feeling tired
- Pulling away from people, almost like hibernating
Read more
Some people with SAD have a period of unusually high energy in early spring or summer. SAD is also more common in people with bipolar II.
Winter blues or SAD?
A dip in mood is common. SAD goes further and affects daily life.
Many people feel a little flatter when the days are short. The winter blues are milder and much more common. SAD goes further: it affects daily life, including how you feel and think.
Read more
About 10% to 20% of people in America may get the winter blues. They are milder than SAD.
Read more
SAD is a type of depression. Professionals look for depressive episodes in a specific season for at least two years in a row, more often than at other times of year. Not everyone has symptoms every single year.
Read more
SAD is linked to daylight, not to the calendar. Stress from holidays or a busy seasonal schedule does not by itself mean SAD.
Who it affects
Anyone can get SAD, but some people are more likely to.
SAD is more common in people who
- Already live with depression, bipolar or another mood condition
- Are young adults, when it usually starts
- Are women, who are diagnosed much more often than men
- Have relatives with SAD, depression or other mental health conditions
- Live far north or far south of the equator, where winter days are short
- Live in cloudy regions
Read more
In the U.S., SAD is more common in places like Alaska or New England than in Texas or Florida.
Read more
SAD often occurs with ADHD, anxiety, eating disorders or panic disorder.
Why does it happen?
Less daylight can upset brain chemistry and your body clock.
The exact cause isn’t known. It is thought to be linked to less daylight in winter, which may affect brain chemicals involved in mood and sleep. Most research has looked at the winter pattern.
Read more
Serotonin and the body’s natural sleep hormone help keep your daily rhythm (circadian rhythm) on track. In SAD, these changes may make it harder to adjust to the shorter days.
Read more
Winter-pattern SAD may involve too much of the body’s own sleep hormone, a natural chemical that makes you sleepy. Summer-pattern SAD may involve too little, though this hasn’t been fully tested.
Read more
Worried or negative thoughts about winter are common in SAD. Researchers aren’t sure whether they are a cause or a result, but they are something therapy can help with.
Read more
People with SAD, especially the winter pattern, may have less serotonin activity. Less sunlight may affect the molecules that keep serotonin at normal levels.
Light therapy and talking therapy
Two well-researched approaches, plus medical options with your provider.
Two approaches with research behind them are light therapy and a version of CBT made for SAD. In one comparison, CBT for SAD worked about as well as light therapy, and its benefits seemed to last longer.
Read more
CBT-SAD is usually two group sessions a week for six weeks. It helps replace negative thoughts about the season with more helpful ones, and uses behavioural activation: planning enjoyable indoor or outdoor activities.
In a study of 177 adults, both treatments helped about equally at first. Two winters later, fewer people who had CBT-SAD had their depression come back (27% compared with 46%).
Read more
Light therapy uses a light box of about 10,000 lux, around 20 times brighter than ordinary indoor light. People usually sit near it for 30 to 45 minutes a day, first thing in the morning, from fall through spring.
Light boxes filter out UV light, so they are safe for most people. People with certain eye conditions, or who take anything that makes them more sensitive to light, should check with a provider first.
If you get a lamp, look for
- About 10,000 lux
- A safety mark from a trusted standards body
- No UV light
Read more
There are also medical treatment options for SAD. These are personal decisions to make with your clinical provider, who knows your health history.
Read more
Talking therapies used for depression in general, like CBT, can also help with SAD. There are no treatments made just for the summer pattern, so general depression care is used.
What helps day to day
Daylight, movement, people and a steady routine.
Small daily habits can make the dark months easier. They work best alongside professional help, not instead of it. On hard days, one small step is enough.
Read more
Drinking too much alcohol or using drugs can worsen SAD symptoms.
Read more
Get as much natural daylight as you can, ideally by going outside every day. Daylight still helps on cloudy days.
Ideas
- Sit near a window to work or eat
- Take a walk at lunchtime, when it’s brightest
- Open curtains as soon as you wake
Read more
Exercise regularly. Cleveland Clinic suggests aiming for 30 minutes at least three times a week.
Read more
Keep up your usual activities and plan things ahead of time, so you don’t end up staying home for long stretches.
Ideas
- A class or club that meets weekly
- A regular film or games night
- Something to look forward to in the darkest month
Read more
Go to bed and wake up at about the same times each day, and avoid phones and other screens right before bed.
Read more
Stay in touch with friends and family rather than pulling away.
Planning ahead for your hard season
Because SAD is predictable, you can get a head start.
Because SAD tends to come at the same time each year, people with a history of it may benefit from starting treatment before the season begins. A provider can help you plan what to do and when. Many people need some support each winter to keep symptoms from coming back.
A simple head-start plan
- Look back: which months were hardest last year, and what were the first signs?
- Book a check-in with your provider a few weeks before that time.
- Line up daylight, movement and social plans for those months.
- Tell one trusted person your early signs, so they can check in.
- Review in spring: what helped, and what will you change next year?
Supporting someone with SAD
Gentle company, daylight together and patience.
When someone you love sinks every winter, it can be hard to watch. You don’t need to fix it. Steady, patient support makes a real difference.
Read more
Keep up your own routines, daylight and connections. Supporting someone is easier when you are looked after too.
Read more
Ideas
- Help with practical needs, like rides to appointments
- Invite them for walks, outings and other activities
- Offer support, understanding, patience and encouragement
- Remind them that with time and treatment, things can get better
Read more
Try
- “Fancy a walk while it’s still light?”
- “I’ve noticed winter seems hard for you. How are you really doing?”
- “Would it help to plan something fun for next month?”
When and where to get help
Signs it’s time to reach out, and help right now.
It may be time to reach out if…
- Each year the same season brings low mood that’s hard to cope with
- People close to you are worried about you
- Things you’ve tried aren’t helping, or treatment isn’t working
- You’re having thoughts of death, suicide or self-harm
- Your mood is getting in the way of work, school, relationships or daily life
Start with a health care provider or mental health specialist. They may ask questions or use a questionnaire, and look at whether your low times keep matching a season. In the U.S., you can also search for treatment at FindTreatment.gov.
📝 Worksheets for this guide
Fill these in privately in the app. Your answers stay on your phone.
Sources
- National Institute of Mental Health (NIMH). Seasonal Affective Disorder
- NHS (UK National Health Service). Seasonal affective disorder (SAD): overview
- Cleveland Clinic. Seasonal Depression (Seasonal Affective Disorder)
- Rohan et al. (peer-reviewed) (2016). Outcomes One and Two Winters Following Cognitive-Behavioral Therapy or Light Therapy for Seasonal Affective Disorder (American Journal of Psychiatry)
- National Institute of Mental Health (NIMH). Depression (publication)
- National Institute of Mental Health (NIMH). Bipolar Disorder (publication)
This guide is for education and self-care. It is not a diagnosis or a substitute for professional care. Please talk to a counselor or clinical provider about your health. Reviewed October 2026.
