Winter blues or seasonal depression? What the research says and what a journal shows

In the late 1980s, researchers from the US National Institute of Mental Health ran a phone survey in one county in Maryland. The numbers were dialed at random and everyone got the same questions: do your mood, sleep, appetite and wish to see people change with the seasons? Nearly everyone said yes. For about one in four, the change was a real problem.

So the winter blues are real and very common. That still doesn't make them a diagnosis. Below: where winter blues end and seasonal depression begins, what is known about light, why memory is a poor witness to last winter, and what to write in a journal so that a month from now you have something to go on. And, separately, when it's time to see a doctor.

92% of respondents noticed seasonal changes in mood and behavior to some degree. For 27%, those changes were a problem. Depending on the definition used, 4.3–10% reported impairment as severe as that of patients with seasonal affective disorder. People felt worst in winter; the summer peak was four and a half times smaller.

The authors drew a conclusion the field still leans on: seasonal affective disorder is the far end of a wide spectrum. At one end, mornings are harder in November. At the other, a depression that comes back at the same time every year.

Winter blues vs seasonal depression: where the line is

Seasonal affective disorder (SAD) was described by Norman Rosenthal and colleagues in 1984. The first paper covered 29 patients, and their depression looked unusual. They didn't lose sleep; they slept more than usual, ate more and craved carbohydrates.

NIMH still lists the same signs for winter-pattern SAD: oversleeping, overeating with carb cravings, and social withdrawal, the feeling of wanting to hibernate. On top of those come the usual symptoms of depression: a low or empty mood most of the day, nearly every day, for at least two weeks; losing interest in things you used to enjoy; guilt, hopelessness, trouble concentrating.

What separates SAD from the blues is how often it returns and how heavy it gets. NHS and NIMH agree on the core: SAD means these episodes arrive at the same time of year for at least two years running, and happen more in that season than at other times. The blues tend to be lighter. Evenings feel like staying in, mornings are slow, but you still care about the things you love and there are good days in between. Treat that as a rough guide for yourself. Only a doctor can make a diagnosis.

There's a third thing that's easy to mix up with the first two. NIMH notes that the "holiday blues" are not SAD. They're driven by the calendar: holidays, family visits, a change in work or school schedules. Seasonal depression follows the length of the day.

How common it is, and whether the north matters

Estimates vary a lot. When Arne Magnusson pooled the epidemiology in 2000, twenty retrospective studies put the share of people with SAD anywhere from 0 to 9.7%. Kasper's own survey shows why: on the same sample, the figure more than doubled depending on the definition.

Intuition says the farther north, the worse. NIMH says as much, comparing Alaska with Florida. A 1999 review by Mersch and colleagues found something messier. North America showed a link with latitude, Europe only a trend, and across all the studies together there was no significant link at all. SAD was also found about twice as often in North America as in Europe. The authors concluded latitude has a small effect, and that climate, genes and social context probably matter more.

Is seasonal depression real, if memory plays tricks?

In 2019 Simon Øverland and colleagues asked an awkward question. Almost every earlier study had asked people directly: "Do you feel worse in winter?" Someone convinced they do will remember exactly that. So the review kept only studies that never mentioned seasons in the questions: mood was measured the normal way, and the dates were checked afterwards.

That left 41 studies. Thirteen found more depression in winter. The rest found no seasonal pattern, a peak at some other time of year, or nothing conclusive. The authors' summary is careful: clinical depression probably does have some seasonality, but a regular dip in mood across the whole population each winter is poorly supported.

There's one practical takeaway for a journal here. "I'm low every fall" is a memory, with all of memory's biases. An entry written on the day doesn't have them. If you note in November how you slept and how you felt, by March you'll be able to see whether this winter really was harder than summer or only seems so in hindsight. That's my reading: the review says nothing about journals, but it describes precisely the problem that writing things down at the time solves.

What is known about light, and what isn't yet

The NHS is blunt about it: nobody knows exactly what causes SAD. The leading idea is that less daylight in winter shifts melatonin and serotonin, and with them mood and sleep. That mechanism hasn't been proven.

Light as a treatment has the same split. In a 2005 meta-analysis by Robert Golden and colleagues, bright light and dawn simulation reduced SAD symptoms, with effect sizes comparable to most antidepressant trials. But only 13% of the studies they found met the quality bar, and the authors themselves warn that many reports of light working rest on weak designs.

That's why the NHS usually doesn't offer light boxes: the evidence is thin, even though many people find they help. It also asks you to talk to a doctor before buying one, because some eye conditions and some medicines make bright light a bad idea. A light box is a decision to make with your doctor.

How to beat the winter blues: what to track

The NHS self-care list for SAD is modest and practical. Get as much daylight as you can and go outside during the day, every day. Keep in touch with friends and family, keep up your usual activities, and go to bed and get up at the same time. A journal adds nothing to that list, but it does show which parts of it you're actually doing.

Two lines a day is enough. Here's what's worth keeping in them, a short set of seasonal depression journal prompts:

Sleep. When you fell asleep and woke up, and whether you felt sleepy in the day. Oversleeping was among the first signs Rosenthal described, and it's easier to spot in entries than by feel.

Light. Did you get outside in daylight today, even for ten minutes? After a week you can count how many days that really happened.

People. Who you talked to face to face. Pulling away from everyone is a sign too, and it creeps in quietly.

One small thing. Something ordinary you managed today: dinner, a workout, replying to an email. Write what already happened; plans can wait.

Mood in one word. "Flat", "anxious", "steady". A word is more precise than a score out of ten, and the mood journal without scores explains why.

If a day felt tense rather than flat, that's worth telling apart. Tiredness after a long week and a seasonal dip look alike, but they point in different directions. There's a separate piece on the stress check-in: one word a day.

Getting through fall and winter when it keeps coming back

The most useful entry gets written in April. When things ease, note what helped: walks at lunch, getting up earlier, a call with a friend on Wednesdays. Early next October, that's the entry to reread first.

It works the other way, too. If last winter's entries show it all started in mid-October, you can start the walks earlier instead of waiting for the slump. The NHS says many people with SAD need treatment every winter to keep symptoms from returning, and last year's notes will help when you talk to a doctor.

What a journal can't do

It can't diagnose you. Two weeks of flat entries don't mean you have depression, and ten bright ones don't mean you don't.

It can't treat anything either. None of the studies above tested journaling as a way to manage SAD, and we're not going to pretend one did.

And it has its own bias. On bad days you write more; on good days you forget to open it. That's why a short entry every day beats a long one once a week: the gaps become visible too.

When the winter blues mean it's time to see a doctor

The NHS suggests seeing a GP if you think you might have SAD, or if you've been diagnosed and treatment isn't helping. NIMH's marker: a low or empty mood most of the day, nearly every day, for two weeks or longer. Add to that losing interest in everything you used to enjoy, feeling guilty or worthless, and changes in sleep or appetite big enough to get in the way of work or school.

If your entries start to include thoughts of death or of hurting yourself, this is no longer about the season. Talk to someone today. Free helplines in your country are listed at findahelpline.com, and in the app Luna doesn't carry on as usual in moments like that; she shows where to turn. What journaling can and can't do for anxiety is covered in does journaling help with anxiety.