Seasonal Affective Disorder in the UK: Symptoms, Treatment, and Coping Strategies

October arrives. The clocks go back. By 4pm, it's already getting dark. You notice you're reaching for carbs more often, struggling to get out of bed, feeling inexplicably flat.

At first, you might dismiss it as tiredness or stress. But as November deepens into December and January drags on, the low mood persists. You're functioning, but everything feels heavier, slower, greyer.

This might be Seasonal Affective Disorder (SAD)—a form of depression that follows a seasonal pattern, typically worsening in autumn and winter.

In the UK, SAD is particularly prevalent. Our northern latitude means dramatically reduced daylight hours from October to March. London receives just 7 hours 50 minutes of daylight on the winter solstice, compared to 16 hours 38 minutes in midsummer. Further north in Scotland, winter days are even shorter.

This isn't just "winter blues." SAD is a recognised mental health condition affecting an estimated 2 million people in the UK, with another 6 million experiencing milder subsyndromal SAD (sometimes called "winter blues").

This guide explains what SAD is, how to recognise it, and—crucially—what evidence-based treatments and strategies can help you navigate the dark months.

TL;DR:

• SAD is a type of depression with a seasonal pattern, typically autumn/winter onset
• Affects 2-3% of UK population severely; 10-20% experience milder symptoms
• Caused by reduced sunlight affecting circadian rhythms, serotonin, and melatonin
• Key symptoms: low mood, fatigue, oversleeping, carb cravings, social withdrawal
• Light therapy is first-line treatment (10,000 lux for 30 mins daily)
• Vitamin D supplementation recommended (especially October-March in UK)
• Other treatments: CBT, medication, lifestyle modifications
• Most people recover fully in spring/summer

What Is Seasonal Affective Disorder?

Seasonal Affective Disorder is a subtype of major depressive disorder or bipolar disorder characterised by recurrent depressive episodes that occur at specific times of year.

Winter-pattern SAD (most common):

• Symptoms begin in autumn (September-November)
• Worsen through winter
• Remit in spring/summer

Summer-pattern SAD (rare):

• Symptoms begin in spring/summer
• Remit in autumn/winter
• Different symptom profile (more agitation, insomnia, poor appetite)

This article focuses on winter-pattern SAD, which accounts for about 90% of cases.

SAD vs Winter Blues

There's a spectrum of seasonal mood changes:

Winter Blues	Subsyndromal SAD	SAD (Clinical)
Mild low mood	Noticeable symptoms	Significant functional impairment
Still functioning well	Some impact on daily life	Difficulty working, socialising, functioning
Self-care usually sufficient	May benefit from intervention	Requires treatment
Very common (~40% of UK)	Common (~10-20%)	Less common (~2-3%)

If symptoms significantly impair your life—you're struggling to work, relationships are suffering, self-care is declining—you may have clinical SAD and should seek professional assessment.

Why Does SAD Happen? The Science

The exact causes aren't fully understood, but several mechanisms are implicated:

1. Reduced Sunlight and Circadian Rhythm Disruption

Sunlight regulates our circadian rhythm—the internal 24-hour clock governing sleep, mood, appetite, and hormone release.

Reduced daylight in winter disrupts this rhythm, particularly affecting:

• Serotonin: Sunlight triggers serotonin production. Lower light = lower serotonin = depressed mood
• Melatonin: Darkness triggers melatonin (sleep hormone). Extended darkness = excess melatonin = fatigue, lethargy
• Cortisol: Cortisol should peak in morning. Disrupted circadian rhythm = dysregulated cortisol = energy problems

2. Vitamin D Deficiency

Vitamin D is synthesised when sunlight (specifically UVB rays) hits skin. In the UK:

• UVB rays are too weak for vitamin D synthesis between October and March
• Even in summer, 40% of UK population has insufficient vitamin D levels
• Vitamin D receptors exist in brain areas regulating mood

Low vitamin D is linked to depression, though whether it's causative or correlational remains debated.

3. Genetic Vulnerability

SAD runs in families. If you have a first-degree relative with SAD, you're 2-3 times more likely to develop it.

Research suggests variations in genes regulating serotonin transporters and circadian rhythm may increase susceptibility.

4. Evolutionary Hypothesis

Some researchers propose SAD might be an evolutionary adaptation—a "hibernation response" that conserved energy during scarce winter months. In modern life, where food is abundant and activity required year-round, this response is maladaptive.

Recognising SAD: Symptoms and Warning Signs

SAD symptoms mirror typical depression but often include distinctive "atypical" features.

Core SAD Symptoms

Mood symptoms:

• Persistent low mood, sadness, or hopelessness
• Loss of interest or pleasure in activities (anhedonia)
• Irritability or anxiety
• Feelings of worthlessness or guilt
• Difficulty concentrating or making decisions

Physical/behavioural symptoms (more distinctive):

• Hypersomnia: Sleeping 2+ hours more than summer; difficulty waking
• Fatigue: Profound tiredness despite extra sleep; "leaden paralysis"
• Increased appetite: Particularly for carbohydrates and sweet foods
• Weight gain: Often 5-10 lbs over winter
• Social withdrawal: "Hibernating"—avoiding friends, cancellling plans

Other symptoms:

• Reduced libido
• Difficulty concentrating ("brain fog")
• Psychomotor slowing (moving/thinking more slowly)
• In severe cases, suicidal thoughts (seek immediate help if present)

When Do Symptoms Start?

Most people notice onset in October or November, as days shorten significantly post-equinox. Symptoms typically peak in December-January and begin lifting in February-March.

For diagnosis, symptoms must:

• Occur in a seasonal pattern for at least 2 consecutive years
• Be significantly more frequent seasonally than non-seasonally
• Remit fully in spring/summer

Who's at Risk? SAD Demographics in the UK

Geography and Latitude

SAD prevalence increases with distance from the equator:

• London (51°N): ~2-3% prevalence
• Edinburgh (56°N): ~4-5% prevalence
• Shetland (60°N): Even higher rates

The further north you live, the more extreme the daylight variation between seasons.

Gender

Women are diagnosed with SAD 4 times more often than men. Reasons may include:

• Hormonal factors (oestrogen interacts with serotonin)
• Greater help-seeking behaviour among women
• Genuine biological vulnerability

Age

SAD typically begins in early adulthood (average onset age 18-30). It's rare in children and older adults, though both can be affected.

Other Risk Factors

• Family history of SAD or depression
• Pre-existing depression or bipolar disorder
• Living far from the equator
• Working indoors with little natural light exposure
• Shift work disrupting circadian rhythms

Diagnosing SAD: When to Seek Help

If you suspect SAD, start with your GP. They'll assess:

1. Symptom pattern: Do symptoms recur seasonally? Remit in summer?
2. Severity: How much do symptoms impact functioning?
3. Differential diagnosis: Rule out other causes (hypothyroidism, chronic fatigue, vitamin deficiencies, etc.)
4. Mental health history: Any previous depression, bipolar disorder, or anxiety?

Your GP may:

• Conduct blood tests (vitamin D, thyroid function, B12, iron)
• Use screening questionnaires (PHQ-9 for depression severity)
• Refer to mental health services if symptoms are severe

Don't wait until you're in crisis. If you recognise the pattern, early intervention (ideally September/October) can prevent full-blown winter depression.

Evidence-Based Treatments for SAD

The good news: SAD is highly treatable. Many people respond well to interventions.

1. Light Therapy (Phototherapy)

Light therapy is the first-line treatment for SAD, recommended by NICE.

How it works: You sit in front of a specialised light box emitting bright light (typically 10,000 lux—about 20 times brighter than typical indoor lighting) for 20-30 minutes daily, usually in the morning.

The bright light compensates for reduced natural sunlight, helping regulate circadian rhythms and boosting serotonin.

Effectiveness:

• 60-80% of people with SAD respond to light therapy
• Improvements often noticed within 1-2 weeks
• Most effective when started early (September/October)

Choosing a SAD lamp: Not all "SAD lamps" are equal. Look for:

• 10,000 lux output at appropriate distance (usually 40-60cm)
• White light (not coloured—UV should be filtered out)
• Large surface area (at least 30x40cm)
• Medical device certification (CE marked)

Recommended brands in UK:

• Lumie Vitamin L
• Beurer TL 90
• Philips EnergyUp
• Lumie Brightspark

Expect to pay £70-£200. Some employers or health insurance may subsidise costs.

How to use:

• Use in morning (within 1 hour of waking) for maximum circadian effect
• Position lamp at eye level, about 16-24 inches away
• You don't need to stare directly—read, eat breakfast, work while exposed
• Start with 15 mins, increase to 30 mins if tolerated
• Use daily from early autumn through to spring

Side effects (rare):

• Headache, eye strain (usually temporary)
• Hypomania (if you have bipolar disorder—consult doctor first)
• Nausea, agitation

Cost via NHS: Light boxes aren't routinely prescribed on NHS but may be available through some mental health services. Private purchase is usually necessary.

2. Vitamin D Supplementation

Public Health England recommends all UK adults take 10 micrograms (400 IU) of vitamin D daily from October to March.

For SAD, higher doses may be beneficial, though evidence is mixed.

Dosage:

• General population: 400-1000 IU (10-25 mcg) daily
• Deficiency treatment: Up to 4000 IU daily (under medical supervision)

Choosing supplements:

• Vitamin D3 (cholecalciferol) is more effective than D2
• Available as tablets, capsules, sprays, or gummies
• Inexpensive (£5-£15 for 3-month supply)

Evidence: Vitamin D alone doesn't "cure" SAD, but correcting deficiency can improve mood and energy, especially when combined with other treatments.

3. Cognitive Behavioural Therapy (CBT)

CBT adapted for SAD (CBT-SAD) helps identify and modify negative thought patterns and behaviours that perpetuate symptoms.

Key components:

• Behavioural activation: Scheduling pleasurable/meaningful activities to counteract withdrawal
• Cognitive restructuring: Challenging unhelpful thoughts ("Winter is unbearable," "I can't cope")
• Relapse prevention: Planning strategies for next winter

Effectiveness: Research shows CBT-SAD produces comparable results to light therapy, with potentially longer-lasting effects (fewer relapses in subsequent winters).

Accessing CBT:

• NHS Talking Therapies (free, but waiting lists 4-18 weeks)
• Private therapy (£50-£100/session)
• Online CBT programmes (some free via NHS apps)

4. Antidepressant Medication

For moderate to severe SAD, antidepressants may be recommended, particularly SSRIs like:

• Sertraline (Lustral)
• Fluoxetine (Prozac)
• Citalopram (Cipramil)

When considered:

• Severe symptoms affecting functioning
• Previous winter depressions
• Insufficient response to light therapy or CBT
• Patient preference

Prophylactic use: Some people take antidepressants preventatively from early autumn through spring, then discontinue in summer.

Effectiveness: Studies show SSRIs effective for SAD, though not necessarily superior to light therapy.

5. Combination Treatments

Many people benefit from combining approaches:

• Light therapy + vitamin D + exercise
• CBT + light therapy
• Antidepressants + light therapy

Discuss with your GP or therapist to find the right combination.

Lifestyle Strategies to Manage SAD

Beyond formal treatments, several lifestyle modifications can significantly help:

1. Maximise Natural Light Exposure

• Get outside daily: Even on cloudy days, outdoor light is brighter than indoor lighting (cloudy day = ~1000 lux; indoor = ~100-500 lux)
• Morning walks: Daylight exposure in first hour after waking is most effective for circadian regulation
• Sit near windows: Rearrange workspace to maximise natural light
• Open curtains/blinds: Let light flood your home
• Trim vegetation blocking windows

2. Exercise Regularly

Exercise is a proven mood booster:

• Releases endorphins and serotonin
• Regulates circadian rhythm
• Combats lethargy

Recommendations:

• 30 mins moderate activity, 5x/week
• Outdoor exercise = double benefit (light + movement)
• Morning exercise = greater circadian benefit

3. Maintain Sleep Hygiene

SAD disrupts sleep-wake cycles. Combat this:

• Consistent schedule: Same bed/wake time daily (yes, weekends too)
• Morning light: Natural light or light box within 1 hour of waking
• Evening dimness: Dim lights 1-2 hours before bed; avoid screens
• Avoid oversleeping: Tempting, but worsens circadian disruption

4. Nutrition

Whilst carb cravings are common, excessive intake can worsen mood through blood sugar crashes.

Strategies:

• Choose complex carbs (wholegrains, legumes) over simple sugars
• Include protein and healthy fats to stabilise blood sugar
• Eat regular meals to maintain energy
• Consider omega-3 supplements (some evidence for mood benefits)

5. Social Connection

SAD promotes withdrawal, creating isolation that worsens depression.

Combat this:

• Schedule regular social activities (even when you don't feel like it)
• Video calls if in-person feels too much
• Join winter groups or classes
• Be honest with friends: "I struggle with SAD; please keep inviting me even if I decline"

6. Plan Winter Activities

Give yourself things to look forward to:

• Book winter weekends away (especially to sunnier climates if budget allows)
• Schedule cultural activities (theatre, cinema, galleries)
• Start a winter hobby (pottery, language class, book club)
• Celebrate winter holidays meaningfully

7. Create a Cosy Environment

Embrace Danish hygge:

• Warm lighting (lamps rather than harsh overhead lights)
• Comfortable, warm spaces
• Candles, soft textures
• Hot drinks, comfort food (in moderation)

The goal isn't to "cure" winter, but to make it bearable, even pleasant.

When to Seek Professional Help

Consider professional support if:

• Symptoms significantly impact work, relationships, or daily functioning
• You've tried self-help strategies for 4-6 weeks without improvement
• You experience suicidal thoughts (seek help immediately—call Samaritans 116 123 or visit A&E)
• Symptoms worsen year-on-year
• You're using alcohol or substances to cope
• You have physical health concerns (unexplained fatigue, pain, etc.)

Early intervention prevents symptoms worsening and teaches skills for managing future winters.

SAD and Other Mental Health Conditions

SAD often coexists with:

• Major depression: SAD can be a seasonal recurrence of underlying depression
• Bipolar disorder: ~25% of people with bipolar experience seasonal mood patterns
• Anxiety disorders: Anxiety often accompanies or worsens with SAD
• Eating disorders: Winter carb cravings can trigger binge eating in vulnerable individuals

If you have pre-existing mental health conditions, discuss seasonal patterns with your mental health provider. Treatment may need adjusting in winter.

FAQs About SAD

Can you get SAD in summer? Yes, though rare (~1% of population). Summer SAD involves different symptoms: insomnia, poor appetite, agitation, anxiety. Causes are less understood.

Does light therapy actually work? Yes. Meta-analyses show light therapy is effective for 60-80% of people with SAD, with effect sizes comparable to antidepressants.

Can I use any bright light? No. Regular household bulbs aren't bright enough (typically <500 lux). You need a medical-grade SAD lamp emitting 10,000 lux with UV filtered out.

Is SAD just vitamin D deficiency? No. Vitamin D deficiency may contribute, but SAD is multifactorial, involving circadian disruption and neurotransmitter changes. Vitamin D alone doesn't cure SAD.

Will moving to a sunnier country cure my SAD? Possibly. Some people relocate and find symptoms resolve. However, moving is drastic, expensive, and involves other life disruptions. Try evidence-based treatments first.

Can children get SAD? Yes, though less common. Symptoms may present as irritability, poor school performance, withdrawal. Consult GP if you suspect SAD in a child.

Does SAD get worse with age? Not necessarily. Some people find symptoms improve with age; others find them worsening. Proactive management helps.

Looking Ahead: Preparing for Next Winter

If you've struggled with SAD this year, prepare proactively for next winter:

August/September:

• Order light box if you don't have one
• Stock up on vitamin D supplements
• Book preventative GP or therapy session

October:

• Start daily light therapy (before symptoms worsen)
• Begin morning outdoor walks
• Schedule social commitments for dark months ahead
• Consider prophylactic antidepressants (discuss with GP)

November-February:

• Maintain all interventions consistently
• Monitor symptoms; adjust treatments as needed
• Be compassionate with yourself during difficult months

March onwards:

• Gradually reduce interventions as daylight increases
• Reflect on what helped this year
• Plan for next autumn

With preparation, each winter can become more manageable.

Finding Hope in the Dark Months

SAD can feel relentless—knowing the darkness will return each year, that you'll struggle through winter after winter.

But with understanding, tools, and support, many people learn to manage SAD effectively. Symptoms become milder. Winters become bearable, even enjoyable in moments.

You're not weak for struggling with seasonal depression. You're responding normally to abnormal conditions (for humans, at least—our ancestors didn't live at 51° north latitude!).

Treatment works. Spring always comes. And each winter you navigate, you learn more about what helps you specifically.

Ready for Support?

If you're struggling with SAD or seasonal low mood and would like professional support, Kicks Therapy offers counselling for depression, anxiety, and seasonal mental health challenges.

We provide in-person therapy in Fulham or online sessions throughout the UK (an excellent way to combine therapeutic support with daylight exposure and movement).

Book a free 15-minute consultation to discuss how therapy can support your mental health through the winter months.

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Kicks Therapy is a BACP-registered counselling service offering integrative humanistic therapy for depression, anxiety, and seasonal mental health difficulties. This article is for information only and doesn't replace medical advice.