Seasonal Affective Disorder (SAD): Symptoms, Causes and Treatment in the UK

Seasonal affective disorder (SAD) is a form of depression that follows a seasonal pattern, usually starting in autumn, deepening over winter and lifting in spring. It is sometimes called “winter depression”, and it is more than just disliking dark evenings: it involves low mood, low energy and other depressive symptoms that recur each year and affect daily life. [1,4]

If you have noticed that you feel consistently flatter, more tired and less motivated once the clocks go back, and that this lifts by summer, this article explains what distinguishes SAD from the more common “winter blues”, what is thought to cause it, and the treatments recommended in the UK, from light therapy to talking therapies and medication.

Winter blues or SAD: what is the difference

Many people in the UK feel a bit lower, sleepier or less sociable once the days shorten. This “winter blues” is common and usually mild. It does not significantly disrupt work, relationships or everyday functioning, and it tends to pass without treatment.

SAD is a recognised type of depression. It involves the same core features as depression: persistent low mood and loss of interest or pleasure in things you usually enjoy, lasting most of the day, most days, over weeks or months, and causing a noticeable impact on your life. [1,4] With SAD, these symptoms follow a seasonal pattern, typically appearing in late autumn or winter and resolving in spring or summer, year after year. [5]

The practical test is impact and duration. Feeling a bit sluggish on a dark Tuesday in November is not the same as weeks of low mood, disrupted sleep and withdrawal from things that matter to you. If you are unsure which applies to you, that uncertainty is itself a good reason to speak to a GP rather than try to self-diagnose.

Symptoms of seasonal affective disorder

According to the NHS, common symptoms of SAD include: [1]

• Persistent low mood
• A lack of interest or pleasure in activities you normally enjoy
• Feeling guilty, hopeless or worthless
• Feeling irritable or restless
• Difficulty concentrating
• Increased appetite, particularly cravings for carbohydrates, and weight gain
• Sleeping more than usual and finding it hard to get up in the morning
• Low energy and feeling sleepy during the day

These last few features, oversleeping, carbohydrate cravings and daytime fatigue, are often more prominent in SAD than in other types of depression, which more commonly involve disturbed sleep and reduced appetite. [4] A minority of people experience the opposite seasonal pattern, with symptoms in summer rather than winter, though this is less common. [1,5]

As with any depression, some people experience thoughts of self-harm or suicide. If this applies to you, please tell a GP, call NHS 111, or if you are in immediate danger call 999. You do not have to wait for a “bad enough” winter to ask for help.

What causes SAD

The exact cause is not fully understood, but the leading explanation links SAD to reduced daylight exposure during autumn and winter. Several related mechanisms have been proposed: [2,3]

• Disrupted circadian rhythm: your body uses light to regulate your internal body clock. Less daylight may disrupt this, affecting sleep, appetite and mood.
• Melatonin changes: melatonin is a hormone that makes you feel sleepy. Some evidence suggests people with SAD produce more of it in winter.
• Serotonin changes: lower sunlight exposure may reduce serotonin, a brain chemical linked to mood regulation; lower serotonin activity is associated with depression.

SAD is thought to be more common in women during the reproductive years and is more frequently diagnosed further from the equator, where winter daylight hours are shorter, which fits with the daylight-based explanation. [5] Having a family history of depression or SAD, or living with another mental health condition that can worsen in winter, may also increase vulnerability. None of this means SAD is inevitable or that it reflects a personal failing; it is a recognised medical condition with effective treatments.

UK winters and why this matters here

In much of the UK, winter daylight is genuinely limited. Parts of Scotland see sunrise after 8.30am and sunset before 3.30pm around the winter solstice, and even southern England has under eight hours of daylight at its shortest. Combined with frequently overcast skies, many people simply get far less natural light exposure between November and February than in summer. This is one reason SAD is a meaningful, seasonal issue for GP practices and therapy services across the country, and why awareness tends to rise sharply in October as the clocks change and evenings draw in.

How SAD is diagnosed

There is no single test for SAD. A GP will usually ask about your mood, sleep, appetite and energy, whether these follow a seasonal pattern that has repeated for at least two consecutive years, and how much they affect your daily life, work and relationships. [1] They may also check for other explanations, such as an underactive thyroid, since some physical health conditions can produce similar symptoms. [1]

It can help to keep a simple diary of your mood, sleep and energy across a few months before your appointment. This is a prompt for a conversation with a professional, not a way to diagnose yourself; only a clinician can confirm what you are experiencing and recommend suitable treatment.

NHS and NICE recommended treatments

Treatment for SAD in the UK generally follows the same framework used for depression more broadly, alongside some SAD-specific options. [6]

Light therapy

Light therapy (phototherapy) uses a specially designed light box that is considerably brighter than ordinary household lighting. You typically sit near it for a set period shortly after waking. The idea is that bright light exposure early in the day may help correct the disrupted circadian signalling thought to underlie SAD. [1,3]

The NHS notes that light therapy is not available on prescription and evidence for how well it works is mixed. Some people find it helpful, particularly when started early in autumn before symptoms set in, while others notice little benefit. [1] If you are considering buying a light box, it is worth discussing this with a GP first, particularly if you have other health conditions, such as a history of mania or hypomania, as any treatment that affects mood regulation needs some care.

Talking therapies, including CBT

Cognitive behavioural therapy (CBT) is a recommended talking therapy for depression, including depression with a seasonal pattern. [6] CBT looks at the links between thoughts, feelings and behaviour, and can help you identify unhelpful patterns, such as avoidance or all-or-nothing thinking, that tend to worsen in winter, and build more sustainable routines around sleep, activity and social contact.

In England, you can usually refer yourself directly to NHS Talking Therapies without needing to see a GP first if you are 18 or over (16 or over in some areas). [1] Waiting times vary by area, so it is worth checking in good time if you know winter tends to be hard for you. If low mood feels bound up with wider life stress rather than the season alone, exploring support through depression therapy may also be relevant.

Medication

For some people, a GP may discuss antidepressant medication, typically an SSRI, as part of managing SAD, usually alongside other approaches rather than as a sole treatment. [6] As with any depression treatment, this is a decision made with a GP based on symptom severity, your history and your preferences; it is not something to start or stop without medical guidance.

A stepped, personal approach

NICE guidance on treating depression in adults emphasises matching treatment intensity to symptom severity and reviewing progress over time, rather than a one-size-fits-all approach. [6] In practice, this might mean starting with self-help and lifestyle measures for milder symptoms, and moving towards structured talking therapy or medication, or a combination, if symptoms are more severe or do not improve.

Daily habits that can help

Alongside professional treatment, several everyday habits are commonly suggested to support mood through winter: [7]

• Get outside in daylight, especially earlier in the day. Even a short walk at lunchtime, when UK daylight is often at its brightest, may help.
• Keep to a regular sleep schedule. Going to bed and waking at consistent times can help counter the pull towards oversleeping.
• Stay physically active. Regular movement, including outdoors where possible, is linked with improved mood in depression generally.
• Plan ahead for low-energy periods. Preparing simple meals in advance or scheduling lighter weeks can reduce pressure when motivation dips.
• Keep some social contact going, even brief or low-key, rather than withdrawing completely.
• Notice and track your pattern. A simple diary can help you and any professional involved see what is working.

These habits are not a replacement for treatment if your symptoms are significant, but they can be a useful foundation alongside it. If low motivation and exhaustion have started to feel like your baseline rather than a winter dip, it may also be worth considering whether burnout therapy fits what you are experiencing, since this can overlap with and intensify a seasonal low.

When to see a GP

Consider seeing a GP if: [1]

• You think you might have SAD and it is affecting your daily life
• You have been diagnosed with SAD before and your usual coping strategies are not working this year
• Low mood is affecting your relationships, work or ability to look after yourself
• You are having thoughts of self-harm or suicide

If you are not sure whether what you are feeling counts as “bad enough”, that question is worth bringing to a professional rather than answering alone. Tools like our Do I need therapy? quiz can help you think through what you are noticing, though they are a starting point for reflection, not a diagnosis.

Frequently asked questions

Is SAD a real medical diagnosis?

Yes. SAD is recognised as a type of depression with a seasonal pattern, and the NHS and Royal College of Psychiatrists both describe it using the same core diagnostic features as depression, plus a recurring seasonal trigger. [1,5] A GP can assess whether your symptoms fit this pattern.

How is SAD different from just hating winter?

Disliking cold, dark weather is extremely common and does not usually affect your ability to function. SAD involves persistent depressive symptoms, low mood, loss of interest, disrupted sleep and appetite, lasting weeks or months and noticeably affecting daily life, which then recur in the same season each year. [1,4]

Does a light box definitely work for SAD?

Not definitely. Some people find light therapy helpful, especially when used consistently and started early in the season, but the NHS notes evidence overall is mixed and it works better for some people than others. [1] It is reasonable to try it alongside, rather than instead of, other treatment if a GP agrees it is suitable for you.

Can SAD happen in summer instead of winter?

Yes, though it is less common. A small proportion of people experience depressive symptoms in spring or summer and feel better in winter. [1,5] The same principle of assessment and treatment applies, adjusted to that pattern.

Do I need antidepressants for SAD?

Not necessarily. Many people manage with light therapy, talking therapy and lifestyle changes, particularly if symptoms are mild to moderate. Medication is one option a GP may discuss, usually guided by how severe and persistent your symptoms are. [6]

Key takeaways

• SAD is a form of depression that follows a seasonal pattern, most often starting in autumn or winter and easing by spring. [1]
• It differs from general “winter blues” through the persistence, duration and daily-life impact of symptoms. [1,4]
• The likely cause involves reduced winter daylight affecting circadian rhythm, melatonin and serotonin. [2,3]
• NHS-recommended treatments include light therapy, talking therapies such as CBT, and medication where appropriate, often used in combination. [1,6]
• Daily habits like daylight exposure, regular sleep and staying active can support other treatment, though they are not a substitute for professional help if symptoms are significant. [7]
• See a GP if symptoms are affecting your life, or urgently if you have thoughts of self-harm or suicide.

Support from MySafeTherapy

If winter consistently brings a heaviness that affects your work, relationships or sense of yourself, you do not have to just wait it out each year. Talking to a therapist can give you a space to understand your pattern, build strategies that fit your life, and work alongside any treatment your GP recommends.

At MySafeTherapy, our BACP, UKCP and NCPS registered therapists offer online sessions that fit around UK working hours, which can make it easier to get consistent support through the darker months.

This article provides general information and does not replace an individual assessment. MySafeTherapy is not an emergency service. If you are in crisis, call 999 or NHS 111, or text SHOUT to 85258.

Sources

[1] NHS. Seasonal affective disorder (SAD)

[2] South London and Maudsley NHS Foundation Trust. Seasonal affective disorder (SAD)

[3] Mayo Clinic. Seasonal affective disorder (SAD) - Diagnosis and treatment

[4] Mental Health Foundation. Seasonal Affective Disorder (SAD)

[5] Royal College of Psychiatrists. Seasonal affective disorder (SAD))

[6] NICE. Depression in adults: treatment and management (NG222)

[7] Mind. Tips for coping with seasonal affective disorder (SAD)

[8] BACP. Seasonal affective disorder: what therapy can help with