Seasonal depression: why your mood drops in autumn and how it is treated

This Sunday, 25 October, at three in the morning the clocks will go back to two. In Palamós the sun will set at 18:53 on Saturday and at 17:51 on Sunday: overnight, one hour less of light in the afternoon. Over the following weeks many people find it harder to get up, feel hungrier and are less keen to see anyone. For most, it passes. Others go through it every year so intensely that it becomes seasonal depression, also called seasonal affective disorder (SAD).

With the clock change coming up, it is worth looking at how a passing slump differs from depression, what is known about the effect of the clock change, why light matters so much, which treatments work (talking therapy, light and medication) and when it makes sense to book an appointment with a psychologist.

What is seasonal depression?

The US National Institute of Mental Health (NIMH) describes it as a type of depression with a recurring seasonal pattern. Symptoms last about four to five months a year, usually from late autumn to spring. There is also a summer form, which is much less common. Diagnostic manuals do not treat it as a separate illness but as depression, or bipolar disorder, with a seasonal pattern, and the pattern has to repeat for at least two years in a row.

How many people have it? A meta-analysis published in 2025, which pooled 24 studies with 32,866 participants, estimated that around 5% of the population meets the criteria for seasonal depression and that another 9% has a milder form, with symptoms that fall short of a diagnosis. The summer form came to about 0.6%. The figures come from a questionnaire rather than clinical interviews, so they should be read as a rough guide.

Who it affects most

According to the NIMH and MedlinePlus, it is considerably more common in women, usually begins in young adulthood and is more frequent in people who have already had depression or who have bipolar disorder, particularly bipolar II. Sometimes several people in the same family have it. The risk also rises in places where winter nights are long, something that needs some nuance on the Costa Brava, as we will see below.

Autumn slump or seasonal depression?

In autumn people often talk about the winter blues, an everyday expression for the tiredness and lack of drive of the first weeks of short days. It is not a medical diagnosis. The MSD Manual describes it like this: many people feel sadder in late autumn and winter, and in some of them the sadness is intense enough to be considered a type of depression. The difference lies in intensity, in duration and in everything you stop doing:

A rough guide only. If you are unsure, a first appointment will help you find out.

There is a third possibility that should not be forgotten: that the tiredness has a physical cause. An underactive thyroid (hypothyroidism), for example, causes tiredness, feeling cold, weight gain and low mood, and it can be ruled out with a simple blood test. We explain it in the article on thyroid problems.

Symptoms of seasonal depression

The underlying symptoms are those of any depression. The UK's NHS lists them like this:

• low mood and a lack of interest in things you usually enjoy;
• feeling guilty, hopeless or worthless;
• feeling restless or irritable;
• difficulty concentrating;
• being hungrier than usual and eating more;
• being more tired and sleeping more than usual;
• thoughts of suicide or self-harm.

What sets it apart from other kinds of depression

In winter depression the body tends to "hibernate". MedlinePlus puts it in one sentence: weight gain and oversleeping are more typical than weight loss and insomnia, which are what usually happens in other forms of depression. The NIMH adds a craving for carbohydrates (bread, pasta, sweets) and social withdrawal. The MSD Manual describes another common complaint: people sleep straight through the night and still feel tired all day.

The symptoms do not arrive all at once. They tend to build up in late autumn and through the winter. In a study of students in Tromsø (Norway) and Ferrara (Italy), most participants in both countries said they felt at their worst in October and November.

Why it appears in autumn

Light and the body clock

The exact cause is not known. The most widely accepted explanation has to do with light: fewer hours of sunshine alter melatonin, the hormone that prepares the body for sleep, and serotonin, which is involved in mood, and with them both sleep and mood. The MSD Manual links it to a mismatch between the circadian rhythm, the body's roughly 24-hour internal clock, and external cues such as the times you get up and go to bed.

It is not as simple as "not enough light" either. A review published in 2010 in the French journal médecine/sciences pointed out that people with seasonal depression get as much light in winter as the rest of the population, so lack of light on its own does not explain everything.

On the Costa Brava too?

Palamós lies at about 42 degrees north. The shortest day of the year, 21 December, has a little over nine hours of daylight, compared with more than fifteen at the end of June. In northern Europe the difference is far greater, and the 2025 meta-analysis confirms that seasonal depression becomes more common the further from the equator people live.

The south is not spared, though. In the Tromsø (69° N) and Ferrara (44° N, not far from our latitude) study, the Italian students reported more changes with the seasons, in mood, sleep or energy, than the Norwegians. The Norwegians had more seasonal depression in winter and spring, and in autumn there was no difference. The authors concluded that latitude alone does not explain it. How much light you actually get matters too: if you work indoors from nine to six, in December you leave after sunset, because in Palamós the sun goes down at around 17:20.

The clock change and your mood

The switch to winter time is this Sunday, 25 October: at 3:00 in the morning it will become 2:00. For a few weeks mornings will be a little lighter and, suddenly, afternoons will have an hour less daylight. Europe has been debating for years whether to scrap the clock changes, but so far nothing has been approved.

What the Danish study found

The most frequently cited work on the subject was published in 2017 in the journal Epidemiology. A Danish team analysed 185,419 hospital contacts for depression between 1995 and 2012 and found that, after the switch to winter time, depressive episodes rose by 11%. The effect faded over about ten weeks. The spring change, by contrast, was not followed by any increase.

The authors offer an explanation: darkness suddenly falling an hour earlier marks the start of a long stretch of short days, and that can weigh on mood. It should be read with caution. Denmark is much further north than Catalonia, the study only counted diagnoses made in hospitals and it shows an association, not that the clock change causes depression. For everyday life it leaves one useful idea: if you know this happens to you, these weeks are a good time to get ahead of it.

How to adjust to the change

Make the most of the extra morning light and go for a walk early. Keep the same wake-up time at weekends too, because regular hours help the body clock. And do not make up for the dark afternoon with screens until late: the NHS advises against using your phone right before going to bed.

How it is diagnosed

There is no test that confirms seasonal depression. A professional makes the diagnosis from a conversation with you: which symptoms you have, since when, how they affect you and whether it has happened in previous years. According to the NIMH, to speak of a seasonal pattern the episodes have to recur in the same season for at least two years in a row and be more frequent than episodes at other times.

What a blood test rules out

Because tiredness and weight gain have other causes, MedlinePlus recommends a physical examination and a blood test to rule out conditions with similar symptoms. The MSD Manual specifically mentions thyroid problems, such as hypothyroidism, and vitamin deficiencies. At Clínica Eupnea, blood tests are done on site, and the family doctor can order and interpret them.

Seasonal depression and bipolar disorder

There is one detail you should mention at your appointment: whether in spring or summer you have periods of high energy, needing little sleep, feeling euphoric or with plans running away with you. Some people with bipolar disorder have a seasonal pattern, with depression in autumn and winter and hypomania in spring and summer, and in that case treatment is different. The NHS also notes that some people have a spell of feeling more energetic than usual at the start of spring or summer. Light itself can, rarely, trigger an episode of mania.

Treatment for seasonal depression

The NHS lists three options: antidepressants, talking therapy such as cognitive behavioural therapy, and light therapy. The choice depends on how severe the depression is. The World Health Organization considers psychological treatments the first option and keeps antidepressants for moderate or severe depression, because mild depression does not need them.

Cognitive behavioural therapy

Cognitive behavioural therapy (CBT) has a version adapted to winter depression. It is done in a group, two sessions a week for six weeks, with two aims: spotting and changing negative thoughts about winter ("I won't have energy for anything until March") and scheduling pleasant activities that get you out of the house, known as behavioural activation.

A University of Vermont trial compared it with light therapy in 177 adults. At the end of treatment both worked equally well: just under half the patients in each group (47.6% and 47.2%) became symptom-free. The difference appeared later. In the first winter there was none, but in the second 27% of those who had therapy relapsed, compared with 46% of the lamp group, and by then only 30% of the latter were still using it. The lead researcher explained it like this: light works while you use it, like blood pressure medication, while therapy leaves you with tools for the winters that follow. At Clínica Eupnea, CBT is one of the approaches used by the psychology service, and it is adapted to each person.

Light therapy at 10,000 lux

Light therapy means sitting every day in front of a lamp that gives off very bright white light. The NIMH refers to 10,000 lux for about 30 to 45 minutes, usually in the morning, from autumn to spring. MedlinePlus adds practical details: about 60 centimetres away, with your eyes open but without looking straight at the light, and starting in autumn, before the symptoms arrive, if it has happened to you in previous years. If it works, the improvement is usually noticeable within three or four weeks.

Lamps made for this purpose filter out ultraviolet light and have nothing to do with a tanning bed. Even so, it is best not to start on your own. It can cause headaches and eye strain, and MedlinePlus advises talking to an eye specialist before starting and avoiding it if you take medicines that increase sensitivity to light, such as some antibiotics, antipsychotics or psoriasis drugs. The NHS, for its part, does not usually offer it because it considers that there is not enough evidence that it works, although it acknowledges that many people find it helpful. If you are thinking about it, mention it at your appointment first.

Antidepressants

When depression is moderate or severe, or does not improve with the above, a doctor may prescribe an antidepressant, alone or alongside therapy. They take four to eight weeks to work. In the United States, the medicines agency (FDA) has approved an extended-release form of bupropion to prevent episodes when taken daily from autumn to early spring. As with any depression, they should not be stopped suddenly, and after a first episode the Catalan health portal Canal Salut recommends continuing them for at least six months after the symptoms have gone.

Psychologists do not prescribe medication. At Clínica Eupnea this is assessed by the family doctor, Dr. Josep Ausio, from the general medicine service, who can also refer you to psychiatry if needed.

What about vitamin D?

It is the question every autumn. According to the NIMH, studies that tested vitamin D as a treatment for seasonal depression have produced mixed results: some found an effect similar to that of light and others found none. If a blood test shows yours is low, it is worth correcting, but it does not replace treatment for depression. We go into detail in the article on low vitamin D in a blood test.

What you can do this autumn

None of these measures replaces treatment when there is depression, but they help everyone and they are the first things the NHS and the WHO recommend:

• Get out into natural daylight every day, ideally in the morning. The NHS advises getting as much natural daylight as you can and going outside in the daytime every day.
• Keep active. You do not need a gym: the WHO gives short walks as an example.
• Keep regular hours for going to bed and getting up, weekends included. If you struggle to sleep, the article on insomnia has practical tips.
• Don't cancel every plan. Staying in touch with friends and family and keeping up your usual activities is part of what the NHS and the WHO recommend, even when the sofa is tempting.
• Go easy on alcohol. According to MedlinePlus, it can make depression worse.
• Put screens away before bed.
• Tell someone you trust how you are feeling.
• Get ahead of it if it happens every year. If you have had bad winters before, book an appointment in autumn, before the worst arrives. The NHS points out that many people need treatment every winter to stop symptoms from coming back.

Myths about seasonal depression

"It's just the winter blues, it will pass." It is true that without treatment the symptoms tend to ease on their own when the season changes. But that can mean four or five months of feeling bad every year, and MedlinePlus warns that it can turn into longer-lasting depression. With treatment, the outlook is good.

"With all the sunshine here, it doesn't exist." It is less common than in northern Europe, but the Ferrara and Tromsø study showed that seasonal changes in mood are not just a Nordic thing. And the light that counts is the light you get, not the light outside while you are in the office.

"Any lamp will do." According to the NIMH, a light therapy lamp gives off light about 20 times brighter than ordinary indoor lighting. A desk lamp is nothing like it, and even with the right lamp it is best to ask first.

"It's a lack of willpower." It is not laziness or weakness of character: it is a disorder that can be treated. Asking for help is not overreacting. Canal Salut points out that, even in developed countries, more than half of people with depression are neither diagnosed nor treated.

When to ask for help

Book an appointment with a psychologist or your doctor if:

• you have felt low almost every day, or have not enjoyed anything, for two weeks or more;
• it happens every autumn or every winter;
• work, studies or home life are suffering;
• you are sleeping or eating much more than usual and cannot change it;
• you turn to alcohol to get through the evenings;
• in spring you have spells of euphoria or very high energy (mention it, because it changes the treatment).

If what stands out is anxiety, restlessness or palpitations, it may be anxiety, which is also treated at the clinic. We explain it in the article on anxiety and stress.

How we help at Clínica Eupnea

In Palamós, the psychology service is made up of two registered psychologists. Sra. Carla Sidro runs the general practice for adults, adolescents and children, which covers depression, anxiety, stress and grief, and Sra. Miruna Mihaila specialises in neuropsychology and geriatric psychology.

Psychology appointments in Palamós

At the first appointment you talk about how you feel, since when and whether it happened in previous winters, and from there a plan is agreed. Sessions last 50 to 60 minutes and can also be held by video call, which is handy when it gets dark early and leaving the house is an effort.

If a physical cause needs to be ruled out or medication considered, the general medicine practice and blood tests are in the same building. To book, call 872 21 75 91 or send a WhatsApp message, Monday to Friday from 9.00 to 13.30 and from 15.30 to 19.30.

Frequently asked questions