.png)
Getting a Head Start on Winter: Understanding Seasonal Depression
Fall officially started last week, and if you live anywhere in the northern half of the country, you've probably already noticed it's getting dark earlier. Right now we're losing a couple of minutes of daylight every day. On November 1 the clocks fall back, and suddenly it's dark by 5.
This is the time of year I start bringing up seasonal depression with patients who've had it before. Not in December, when they're already sleeping ten hours and can't get off the couch. Now, while there's still time to get ahead of it.
Seasonal depression is one of the few forms of depression where we can see it coming on a calendar. That makes it unusually preventable, and I think that's worth taking advantage of.
Winter blues or seasonal depression?
Most people feel a little flatter in winter. Less energy, more time indoors, a stronger pull toward carbs and early bedtimes. Somewhere around 10 to 20% of adults get a mild version of this, and it usually doesn't need treatment.
Seasonal affective disorder (SAD) is different. It's a true major depression that follows the calendar. The formal name is major depressive disorder with a seasonal pattern, and the diagnosis requires the episodes to start and lift around the same time of year for at least two years in a row. About 5% of U.S. adults have it, and for them it can take up four or five months of every year.
The question I ask to tell the two apart is simple: is it changing what you can do? Feeling sluggish in January is the blues. Missing work, dropping friends, and not recognizing yourself until April is something we should treat.
Why less light affects mood
The short answer is that your brain uses light to keep time. Morning light hits specialized cells in the retina that report straight to the body's master clock, a small cluster of neurons in the hypothalamus called the suprachiasmatic nucleus. That clock sets the timing for sleep, hormones, body temperature, and appetite.
When mornings get darker, that signal gets weaker and later. Two things follow:
Melatonin runs long. Melatonin is the hormone that tells your body it's night. In people with SAD, its nightly release tends to drift later and last longer, which is part of why winter depression looks so much like hibernation: sleeping more, craving carbohydrates, gaining weight, wanting to be left alone.
Serotonin activity drops. Serotonin is one of the brain's main mood-regulating chemical messengers. Studies suggest people with SAD have more serotonin transporter activity in winter, meaning serotonin gets cleared from the gap between neurons faster and does less work.
You'll also hear a lot about vitamin D, since we make less of it with less sun. It's a reasonable theory, and I check levels when it makes sense. I wouldn't oversell supplements as a treatment for SAD, though. The evidence is mixed, and in trials vitamin D hasn't reliably prevented or treated it.
One detail I find useful for patients: the classic winter pattern looks different from typical depression. Many depressive episodes involve insomnia or reduced appetite, while winter SAD often runs in the opposite direction. If you tend to sleep more and eat more as the days shorten, that's worth paying attention to.
What to watch for, and who's more at risk
Winter SAD tends to creep in over October and November rather than arriving all at once. The early signs are easy to write off as "just being tired":
Sleeping more but not feeling rested
Heavier appetite, especially for carbohydrates, and some weight gain
Low energy and a heavy, slowed-down feeling in your body
Pulling back from people and plans you'd normally enjoy
Trouble concentrating, and a mood that stays low most days
Some people are more likely to get it. SAD is more common in women, usually starts between ages 18 and 30, and becomes more common the farther north you live. It also shows up more often alongside bipolar II disorder, ADHD, and anxiety disorders, and in people with family members who have depression.
The bipolar piece matters for treatment. For a small group of people, the seasonal shift runs both ways: depressed in winter, and more energized than usual, sometimes hypomanic, in spring. Bright light and antidepressants can both push someone with bipolar disorder toward hypomania. If your springs look like that, tell your prescriber before you start anything.
What about supplements?
Supplements come up a lot this time of year, especially vitamin D. I think they can be useful, but I see them as supportive rather than a substitute for light therapy, therapy, or medication when someone has true seasonal depression.
Vitamin D is the obvious one. Levels tend to fall during the winter, particularly in people who live farther north, and if your level is low, replacing it makes sense. What I would not do is assume that taking more vitamin D will prevent seasonal depression on its own. The research specifically looking at vitamin D for SAD has been mixed.
Omega-3s are another supplement I sometimes discuss, particularly for people who do not eat much fatty fish. There is some evidence for a modest benefit in depression more broadly, although we do not have good evidence that omega-3s specifically prevent seasonal depression.
Magnesium can be useful when sleep, muscle tension, or anxiety are part of the picture. For people whose winter symptoms are mostly fatigue, low motivation, or brain fog, I also think it is worth looking at the basics before reaching for an “energy” supplement: vitamin B12, iron, thyroid function, vitamin D, sleep, and nutrition. Creatine is another supplement getting increasing attention for both physical and cognitive energy and as a possible adjunct in depression, although I would still consider it supportive rather than a treatment for SAD itself.
I am more cautious with products marketed specifically as “mood boosters” or “energy boosters.” St. John’s wort has significant medication interactions, and stimulating herbal blends can make anxiety or insomnia worse. Melatonin can be useful for circadian timing, but timing matters; taking it indiscriminately can actually make daytime sleepiness worse.
If you want to use supplements as part of your winter routine, I generally prefer targeted choices based on your symptoms, diet, medications, and lab work rather than a large all-in-one mood formula.
For patients who ask which products and formulations I typically recommend, I keep a curated Fullscript collection here:
Getting ahead of it this fall
If you've had seasonal depression before, early fall is the window. It's much easier to hold on to a good mood than to climb back out of a bad one in January.
Protect your mornings. Get outside within an hour or so of waking, even on cloudy days. Overcast daylight is still far brighter than indoor lighting. Keep your wake time consistent, including weekends, so your internal clock has something steady to anchor to.
Keep moving and keep your plans. The pull in winter SAD is toward withdrawal, and withdrawal feeds the depression. Scheduling things you enjoy before you feel like doing them is the core of behavioral activation, one of the most useful tools we have.
Consider a light box. Light therapy is a first-line treatment for winter SAD. The standard is 10,000 lux, used for about 20 to 45 minutes shortly after waking, sitting a foot or two away with the light off to the side rather than staring into it. People often notice a difference within a few days to two weeks. Look for a box that filters UV, and skip tanning beds entirely. If you have a retinal condition or diabetes-related eye disease, check with your eye doctor first.
The real problem with light boxes is adherence. In one well-known trial, only about a third of people assigned to light therapy were still using it in later winters. It works when you use it, and a lot of people stop.
Therapy built for SAD. There's a version of cognitive behavioral therapy designed specifically for seasonal depression, called CBT-SAD. It focuses on behavioral activation and on reworking beliefs like "winter is unbearable." In a trial of 177 adults, it worked about as well as light therapy the first winter. Two winters later, depression had come back in 27% of the CBT group compared with 46% of the light therapy group. I find that one of the more compelling findings in this area: skills stick around in a way a device on your kitchen table doesn't.
Medication, started early. Bupropion XL (Wellbutrin XL) is FDA-approved to prevent seasonal depressive episodes. In three trials with 1,042 people, it was started in early autumn while patients were still feeling well and continued until spring. Recurrence dropped from roughly 21 to 31% on placebo to 13 to 19% on bupropion. It's also a reasonable fit for the winter pattern: bupropion works on dopamine and norepinephrine rather than serotonin, so it tends to be activating rather than sedating, and it's less likely to cause weight gain. Some people with SAD do well on an SSRI instead. The point is timing. If medication has helped you before, fall is when to talk about restarting it, not after you're already depressed.
Option | When to start | What the evidence shows |
Morning light, steady routine, activity | Now | Low risk, sensible, not well studied as prevention on its own |
Light box (10,000 lux) | Early fall or at first symptoms | First-line treatment; many people stop using it |
CBT-SAD | Fall, before or during symptoms | Matches light therapy short term; fewer relapses two winters out |
Bupropion XL | Early fall, while still well | FDA-approved for prevention; about 44% lower relative risk of recurrence |
Selected supplements for SAD | Based on symptoms or lab results | May support sleep, energy, or nutritional deficiencies; not a primary treatment for SAD |
When to bring it up
If last winter was hard, and especially if the past two or three were, bring it up at your next appointment this fall rather than waiting to see how things go. That conversation is short when you're feeling well. It's a lot harder in February.
And if you're already noticing the signs above for more than a couple of weeks, don't wait for them to become obvious. If you ever have thoughts of harming yourself, call or text 988 to reach the Suicide & Crisis Lifeline.
If you know your depression shows up in November, tell your prescriber in September or October. Prevention only works if we start before the episode does.
Comments