Seasonal Affective Disorder in 2026. How to Tell Winter Blues From Winter Depression, and What Works
Seasonal affective disorder, often called SAD or winter depression, is depression that returns at the same time each year, usually starting in autumn and lifting in spring. Feeling a little flatter in the dark months is common. SAD is different, because it meets the criteria for depression, including persistent low mood, loss of interest, low energy, oversleeping, craving carbohydrates and weight gain, and it affects work and relationships. The evidence on treatment is clearer than most people realise. A 2020 meta-analysis of 19 randomised trials in Psychotherapy and Psychosomatics found that bright light therapy improved symptoms and increased the chance of response, though the trials were small. NICE notes that the evidence for light therapy is less certain than for talking therapies and antidepressants, and treats seasonal depression in the same way as other depression. Vitamin D is often suggested, but the VITAL-DEP trial of 18,353 adults found that vitamin D supplements did not prevent depression or improve mood. Physical causes such as an underactive thyroid, iron deficiency and low B12 can feel identical and should be checked. At The Wellness a doctor can assess you by video from £150, subject to availability, check the physical causes, start treatment and arrange psychiatry where specialist input is needed. Fees appear further down this page.
Reviewed by the medical team at The Wellness. Last updated 9 October 2026.
Book a confidential video appointment on WhatsApp or email team@thewellnesslondon.com or call 020 3951 3429.
Key facts about seasonal affective disorder
SAD is depression with a seasonal pattern, usually autumn and winter, recurring in at least 2 consecutive years.
Oversleeping, carbohydrate craving and weight gain are more typical than in other depression.
Bright light therapy helps many people, though the trials are small, and it is not suitable for everyone.
Vitamin D supplements did not prevent depression in a large trial of 18,353 adults.
Talking therapies and antidepressants are effective, as for other depression.
If you have thoughts of harming yourself, call 999 or Samaritans free on 116 123, at any time.
Is it the winter blues or seasonal affective disorder
Many people feel more tired and less motivated when the days are short. That is normal and passes without affecting daily life very much.
Seasonal affective disorder is depression. It lasts most days for at least 2 weeks, includes low mood or loss of interest, and interferes with work, relationships or looking after yourself. Common symptoms include sleeping much more but still feeling tired, craving sugary and starchy food, gaining weight, withdrawing from people, and difficulty concentrating.
The seasonal pattern is confirmed when episodes start and end at about the same time of year, in at least 2 consecutive years, without similar episodes at other times.
What causes seasonal affective disorder
The main explanation is reduced daylight affecting the body clock, alongside changes in melatonin, which regulates sleep, and serotonin, which affects mood. People living further from the equator are more often affected, and London’s short winter days make it a familiar problem here.
A family history of depression, a personal history of depression or bipolar disorder, and being younger and female all increase the chance of SAD.
Ask a doctor about your symptoms on WhatsApp or email team@thewellnesslondon.com.
Which physical causes should be checked
An underactive thyroid causes tiredness, low mood, weight gain and feeling cold, and can be mistaken for winter depression. Iron deficiency, low vitamin B12 and folate, diabetes, sleep apnoea and, in women, perimenopause can produce similar symptoms.
A blood panel including full blood count, ferritin, thyroid function, B12, folate, HbA1c and vitamin D separates these causes in most people. Correcting a low vitamin D is worthwhile for bone and muscle health, even though the evidence does not show it treats depression.
Does light therapy work
Light therapy means sitting near a special light box, usually 10,000 lux, for around 30 minutes each morning, starting in early autumn. A 2020 meta-analysis of 19 randomised trials found it improved depression scores and increased the chance of responding to treatment, though the authors noted that the trials were small and varied.
It is not right for everyone. People with bipolar disorder should use it only under medical supervision, because it can trigger hypomania or mania. People with eye conditions or taking medicines that increase sensitivity to light should check with a doctor first. Side effects include headache, eye strain and difficulty sleeping if used late in the day.
What other treatments are effective
Talking therapies. Cognitive behavioural therapy is effective for depression, including depression with a seasonal pattern, and a version tailored to SAD has been studied with good results.
Antidepressants. NICE recommends treating seasonal depression in the same way as other depression. Some people start an antidepressant before their usual time of onset each year, by agreement with their doctor.
Daylight, activity and routine. A morning walk outside, regular exercise, a consistent wake time and keeping in contact with people all help, and make other treatments work better.
When do you need help urgently
Call 999 or go to A&E if you have thoughts of ending your life and feel you may act on them. You can also call NHS 111 and select the mental health option, or Samaritans free on 116 123, at any time.
Book a same-day appointment if you are struggling to function, are not sleeping or eating, are drinking more to cope, or feel very different from your usual self.
What does private care for seasonal depression cost in London
Membership practices in central London charge annual retainers running into thousands and then £400 to £600 or more per visit, Harley Street GP consultations sit at £250 to £350, and private psychiatry first appointments commonly cost more.
Video consultations are from £150; confirm fees for other services, any prescription or referral charges, and what is covered before booking.
Signature Membership: enquire about fees, access and terms before joining.
Psychiatrist consultation for depression assessment and medication review: enquire about fees before booking.
Comprehensive Blood Panel with consultation, checking thyroid, iron, B12, folate, HbA1c and vitamin D: confirm the fee and tests covered before booking.
Extended 45-minute consultation: confirm the fee before booking.
In-person consultation, 30 minutes: confirm the fee before booking. Video consultations are from £150, subject to availability.
Appointments are available 7 days a week by video, or at our London clinics, including Marylebone and Belgravia.
Why patients choose The Wellness for low mood in winter
Because you can consult by video from home, subject to availability.
Because physical causes are checked first, including thyroid, iron and B12.
Because treatment is based on evidence, from talking therapies and medication to light therapy where it suits you.
Because a consultant psychiatrist is available when specialist input is needed.
And because it is confidential, with nothing shared with an employer or insurer without your consent.
Related reading
Private mental health care covers anxiety and depression, burnout covers exhaustion linked to work, always tired and blood tests covers the physical causes of fatigue, and ran out of antidepressants while travelling covers getting medication in London.
Ask about appointment availability on WhatsApp or call 020 3951 3429.
Frequently asked questions
What are the symptoms of seasonal affective disorder
Persistent low mood or loss of interest, low energy, sleeping more, craving carbohydrates, weight gain, difficulty concentrating and withdrawing from people, starting in autumn or winter and lifting in spring.
Does vitamin D help seasonal depression
The VITAL-DEP trial of 18,353 adults found that vitamin D supplements did not prevent depression or improve mood. Correcting a deficiency is still worthwhile for bone and muscle health.
Does a SAD lamp work
A 2020 meta-analysis of 19 trials found that bright light therapy improved symptoms, although the trials were small. It is usually used at 10,000 lux for around 30 minutes each morning, and people with bipolar disorder should use it only under medical supervision.
Can I get antidepressants for seasonal affective disorder
Yes. NICE recommends treating seasonal depression in the same way as other depression, and a doctor can discuss whether medication, talking therapy or both suit you.
Can I see a doctor about depression online
Yes. A video consultation with a doctor can assess your symptoms, arrange blood tests, start treatment and refer you to a psychiatrist where needed.
How much does a private doctor appointment for depression cost
At The Wellness video consultations are from £150; extended consultation and psychiatry fees are confirmed before booking.
The Wellness is a doctor-led private healthcare group providing medical care from our London clinics, including Marylebone and Belgravia. All doctors are GMC-registered. Prescriptions are issued only following a consultation and clinical assessment. Blood analysis is performed by accredited laboratories. In an emergency call 999. This article is general information and not a substitute for medical advice about your own health.
Enquire now on WhatsApp or email team@thewellnesslondon.com or call 020 3951 3429.
References
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