SAD (Seasonal Affective Disorder): Why it happens and how to cope

Seasonal depression, or seasonal affective disorder (SAD), is depression that returns at the same time each year. For most people it starts in late fall and lifts in spring. It’s a recognized form of major depression, and it responds well to treatment.

In Massachusetts, the timing is predictable. The clocks fall back on November 1, and by the winter solstice Boston gets about nine hours of daylight, with the sun down by 4:14 p.m.¹ If your mood tracks that curve every year, it’s worth taking seriously now, before December.

Rockland Recovery Behavioral Health treats seasonal depression through our depression treatment program in Sharon, MA, in person or by telehealth anywhere in the state. Call 855.520.0531 to talk it through.

What is seasonal depression?

Clinically, SAD is major depression with a seasonal pattern. The symptoms are the same as other depression. What sets it apart is the calendar: episodes start and end around the same seasons, and a diagnosis requires that pattern for at least two consecutive years.²

So yes, seasonal depression is real. It isn’t a mood you can snap out of, and it isn’t the same as disliking winter.

When does seasonal depression start?

For the winter pattern, symptoms usually begin in late September through November, peak from December to February, and ease in March or April as days lengthen. NIMH describes symptoms lasting about four to five months a year.²

Many people notice the first signs right after the time change, when evening commutes suddenly happen in the dark. That early window is also the best time to act. Light therapy and preventive medication are both meant to start in the fall, before the hardest months arrive.

A smaller group has the reverse pattern, with depression starting in late spring or summer and lifting in fall.

Symptoms of seasonal depression

SAD includes the core symptoms of depression: low mood most of the day, loss of interest, trouble concentrating, fatigue, and feeling hopeless or worthless. On top of those, each pattern has its own signature.²

Winter pattern:

• Sleeping much more than usual and still waking tired
• Carbohydrate cravings and weight gain
• Pulling away from people, sometimes described as “hibernating”
• Heavy, slowed-down limbs

Summer pattern:

• Trouble sleeping
• Poor appetite and weight loss
• Restlessness, agitation, or anxiety

If the main thing you notice is that nothing feels good anymore, read our post on anhedonia. It’s one of the most common ways winter depression shows up.

Winter blues or seasonal depression?

The winter blues are common and mild. You feel a little flatter, a little more tired, and you’d rather stay in, but work, relationships, and the things you enjoy still hold.

Seasonal depression gets in the way of your life. Signs you’ve crossed that line:

• Low mood most days for two weeks or longer
• You’re missing work, falling behind, or canceling on people regularly
• Sleep and appetite have changed in ways other people notice
• The same slide happened last winter, and maybe the one before

If exhaustion is the loudest symptom and it’s tied to your job, our comparison of burnout vs. depression can help you sort out which one you’re dealing with.

What causes seasonal depression?

Less daylight changes the chemistry that regulates mood and sleep. Researchers point to three connected shifts:²

• Serotonin. People with SAD show reduced serotonin activity in winter, and sunlight helps regulate it.
• Melatonin. Winter-pattern SAD is linked to producing too much melatonin, the hormone that makes you sleepy.
• Circadian rhythm. Together, those changes knock your internal clock out of step with your actual day.

Vitamin D may play a role too, since it supports serotonin activity and levels drop when you’re indoors all winter.

Risk is higher for women, for people who live farther north, and for people who already have depression or bipolar disorder, especially bipolar II.² Massachusetts sits far enough north that short winter days are a real factor.

How seasonal depression is treated

Four treatments have the strongest evidence. Many people use two or more together.

Light therapy

Sitting in front of a 10,000-lux light box every morning is a first-line treatment for winter-pattern SAD, and it often starts working within days to a couple of weeks.³ It works through light entering the eyes, which helps reset your internal clock. Instructions for using one are below.

Cognitive behavioral therapy

Cognitive behavioral therapy (CBT) targets the thoughts and habits that deepen a winter slump, like “there’s no point going out, it’s dark anyway.” A version adapted for SAD, called CBT-SAD, pairs that work with planning activities you’ll still do in winter.

CBT also appears to hold up longer than light therapy. In a study of 177 adults, 27% of people treated with CBT-SAD had symptoms return by the second winter, compared with 46% of those treated with light therapy alone.⁴

Medication

Antidepressants can help, and extended-release bupropion is FDA-approved to prevent winter episodes when taken daily from fall through early spring.² Our prescribers provide medication management alongside therapy, so medication decisions happen in the same place as the rest of your care.

Vitamin D

The evidence is mixed. Some studies find it as effective as light therapy and others find no effect.² A simple blood test tells you whether you’re low, and your doctor can recommend a dose if you are.

Levels of care

Most people with seasonal depression do well with weekly outpatient therapy, in person or by telehealth, which matters on icy February mornings. If winter depression is severe or has you struggling to function, our intensive outpatient program (IOP) offers several sessions a week while you keep living at home.

How to use a light box for seasonal depression

1. Buy one made for SAD. Look for 10,000 lux at the recommended distance and a design that filters out UV light.³ Skip lamps that don’t list their lux rating.
2. Use it within an hour of waking. Morning light does the most to reset your internal clock. Evening use can disrupt sleep.
3. Sit 16 to 24 inches away for 20 to 30 minutes. Keep your eyes open, but don’t stare into it. Eat breakfast or read while it runs.³
4. Start in early fall. The standard approach is daily use from fall through spring, beginning before symptoms settle in.²
5. Talk to a clinician first if you have bipolar disorder or an eye condition. Too much light too fast can trigger manic symptoms, and conditions like glaucoma or diabetic eye damage need an eye doctor’s input.³

If you have a history of mood swings in both directions, our bipolar disorder treatment program can help you build a winter plan that’s safe for you.

What you can do this fall

• Get outside in the morning. Even a 20-minute walk under an overcast sky delivers more light than most indoor rooms.
• Keep your wake-up time fixed. Sleeping in on dark weekends makes Monday mornings harder for your body clock.
• Book winter plans now. A standing weekly dinner or class is easier to keep than a spontaneous one when it’s dark at 4:30.
• Move your workspace toward a window. Small changes in daily light exposure add up.
• Tell someone what last winter was like. A partner or friend who knows the pattern can spot it early.

When to get help

Reach out if symptoms have lasted two weeks or more, if you’re having trouble keeping up with work or home, or if the pattern keeps repeating year after year. Starting therapy in October gives you tools before the hardest stretch instead of during it.

If you’re having thoughts of suicide or feel hopeless about getting through the winter, call or text 988 to reach the Suicide and Crisis Lifeline any time.

Frequently asked questions

Is seasonal depression real?

Yes. It’s classified as major depressive disorder with a seasonal pattern, and it’s diagnosed when depression follows the seasons for at least two years in a row. It’s more than a dislike of cold weather.

Does vitamin D help with seasonal depression?

It might, especially if you’re deficient. Research results are mixed, so get your level checked rather than guessing at a dose, and treat vitamin D as an add-on rather than a replacement for therapy or light therapy.

Do tanning beds help with seasonal depression?

No. Light therapy works through light reaching your eyes, and therapeutic light boxes are designed to filter out UV. Tanning beds deliver concentrated UV to your skin, which raises skin cancer risk without providing the treatment that helps SAD.

Does red light therapy help with seasonal depression?

The evidence for SAD comes from bright white light boxes rated at 10,000 lux. Red light devices are built for different purposes and haven’t been shown to replace a standard light box. If you’re buying a device for seasonal depression, check the lux rating before anything else.

Get help for seasonal depression in Massachusetts

Seasonal depression is predictable, which means you can plan for it. Call Rockland Recovery Behavioral Health at 855.520.0531, reach us through our contact page, or verify your insurance online. We’re at 374 Old Post Road, Sharon, MA 02067, with telehealth available statewide.

Footnotes:

1. Sunrise and sunset times for Boston, MA, December 21, 2026 — Old Farmer’s Almanac
2. Seasonal Affective Disorder — National Institute of Mental Health
3. Seasonal affective disorder treatment: Choosing a light box — Mayo Clinic
4. Rohan KJ, et al. Outcomes one and two winters following cognitive-behavioral therapy or light therapy for seasonal affective disorder. American Journal of Psychiatry, 2016