Seasonal affective disorder

Also called SAD, Winter depression

Depression with a seasonal pattern, not a low mood about the weather. Treatable, and worth treating before the winter starts rather than during it.

What it is

Depression that follows a seasonal pattern, most often starting in autumn and lifting in spring. It is a recognised specifier of depression rather than a separate illness.

The likely mechanism is reduced light affecting the body clock and the hormones it drives, which is consistent with it being more common the further north people live. In the UK that is not a small effect.

The symptom pattern is often the reverse of typical depression: sleeping more rather than less, eating more rather than less, craving carbohydrates, and gaining weight over winter.

A milder form, sometimes called the winter blues, affects a much larger number of people and responds to the same measures.

It matters clinically because the timing is predictable, which almost nothing else in mental health is. Treatment started in early autumn works better than treatment started in January.

Signs you might notice

Persistent low mood through autumn and winter, lifting in spring, for two years or more in the same pattern.

Sleeping much more than usual and still feeling unrefreshed.

Increased appetite, carbohydrate craving, and winter weight gain.

Loss of interest and enjoyment, low energy, difficulty concentrating.

Irritability, and feeling heavy in the arms and legs.

Withdrawal from other people.

If there are thoughts of suicide, this is depression and needs treating urgently regardless of the season. See suicidal thoughts.

Worth checking rather than assuming: hypothyroidism, anaemia and vitamin D deficiency all produce a similar winter picture and are all simple blood tests.

How it can affect day-to-day life

Being told to cheer up because it is only the weather is what most people get, and it is why many never mention it to a clinician.

For people who work indoors through the dark months, the practical reality is not seeing daylight at all on a weekday, which is worth naming as the mechanism rather than a lifestyle failing.

Light therapy boxes work for a proportion of people and need to be the right specification, at least 10,000 lux, used in the morning for around 30 minutes, at the right distance. Most people who say it did not work were using it wrongly or too late in the day.

Light boxes are not suitable for everyone, including some eye conditions and people with bipolar disorder, where they can trigger a mood swing. Ask first.

The pattern is predictable enough to plan around, which is genuinely useful: booking the therapy, starting the treatment, and arranging the winter routine in September rather than December.

Supporting someone well

Start before it starts. Late summer and early autumn is when the plan should be made.

Get outside in daylight, especially in the morning. Twenty minutes outdoors beats an hour by a window.

Try light therapy properly: 10,000 lux, mornings, 20 to 30 minutes, at the distance the manufacturer specifies. Check first with a clinician if there is an eye condition or bipolar disorder.

Keep the sleep and wake times steady rather than sleeping in through the winter.

Exercise, ideally outdoors and ideally in daylight.

Ask for talking therapy. In England you can self-refer to NHS Talking Therapies and say the pattern is seasonal.

Antidepressants work, and starting them in early autumn is the recognised approach for a well-established pattern.

Have the blood tests, so a thyroid problem is not being treated as a season.

Where to get help

A GP practice, or self-referral to NHS Talking Therapies in England.

Mind have clear information on SAD and on light therapy.

Seasonal Affective Disorder Association for specific guidance on light treatment.

Samaritans on 116 123, any time.