Also called: Seasonal affective disorder; SAD; winter blues; seasonal depression
Relief and prevention
Strength
Mood, energy and motivation that fall reliably as the days shorten and lift again in spring. Shorter days shift the body clock in people who are sensitive to it - and the natural response, staying indoors and moving less, deepens exactly what it is responding to.
How common: Full seasonal depression in 1-10% of adults depending on latitude, with milder winter slumps in another 10-20%
What it is
Seasonal affective disorder is depression with a seasonal pattern, most commonly winter onset. The leading explanation is a phase shift in the circadian clock caused by later dawn and less light, together with changes in serotonin signalling in people who are sensitive to the seasonal swing.
It has a characteristic shape that distinguishes it from other depression: rather than losing sleep and appetite, people typically sleep more, crave carbohydrate, gain weight and feel heavy and slowed. Milder subsyndromal winter blues is far more common than the full disorder.
What it feels like
- Mood and energy dropping predictably from autumn onward
- Sleeping more than usual and still waking unrefreshed
- Craving carbohydrate, and gaining weight over the winter
- Heavy limbs, slowed thinking, and everything feeling like more effort
- Lifting reliably in spring, which is the pattern that identifies it
What causes it
Most people have more than one of these at once, and they feed each other. Read the
list looking for the two or three that sound like your week rather than for the one
true answer — the ones that describe you are the ones worth acting on.
- A phase-shifted body clock
- Later dawn delays the circadian signal, so the internal clock drifts out of step with the day. That mismatch produces the sleepiness, the low mood and the difficulty getting going in the morning.
- Reduced light exposure overall
- Indoor light is a fraction of outdoor light even on a dull day. A winter spent commuting in the dark at both ends means the eyes receive almost no genuinely bright light for months.
- Altered serotonin signalling
- Serotonin transporter activity varies seasonally and does so more in people with seasonal depression, which is part of why serotonergic treatments and bright light both help.
- Melatonin timing
- Melatonin release starts earlier and lasts longer in longer nights. In sensitive people the resulting duration signal produces the slowed, sleepy, heavy pattern.
- Reduced activity in cold and dark
- Everything about winter discourages going out and moving. Exercise falls at exactly the point it is most needed, which removes one of the two levers with good evidence.
- Vitamin D deficiency
- Vitamin D falls over winter at higher latitudes and is associated with low mood, though whether correcting it improves seasonal depression specifically is less clear than the association suggests.
- Latitude
- Prevalence rises with distance from the equator, which is about as clean a demonstration of the light mechanism as could be asked for.
- Sensitivity rather than exposure
- Everyone gets the same winter. What varies is the response, which is why some people are unaffected in Scandinavia and others struggle in mild climates.
- Social withdrawal
- Winter reduces contact, and isolation independently worsens mood. The season removes activity and company at the same time.
Who tends to get it
- Anyone living at higher latitudes with short winter days
- People with a history of depression, in whom the seasonal pattern is more likely
- Anyone whose commute is in darkness at both ends
- Women, in whom seasonal affective disorder is diagnosed more frequently
- People whose activity falls sharply over winter
What makes it worse, and what settles it
Makes it worse
- Staying indoors all day, particularly on the few bright winter mornings
- Stopping exercise over winter
- Irregular sleep and late lie-ins at weekends, which shift the clock further
- Alcohol, which worsens both mood and sleep
- Waiting for spring, which is a long time to feel like this
Settles it
- Morning light - outdoors within an hour of waking, or a bright light box used first thing, which has the best evidence of anything here
- Regular exercise, ideally outdoors and in the morning, which combines both levers
- A consistent wake time through the winter, which anchors the clock
- Getting outside at lunchtime, which is the brightest available option for most people
- Keeping social contact up deliberately rather than letting it lapse
What actually helps
The short version: Shorter days shift the body clock and lower serotonin signalling in people who are sensitive to it; energy, sleep and appetite change, and the natural response - staying indoors and moving less - deepens it. Morning light and movement are the two levers with evidence
Strength work: Walking - outdoors, in the morning, whatever the weather; Full Body; Weight Training; High-Intensity Interval Training - the antidepressant dose of exercise is about 30 minutes most days, and a hard session counts double
Stretching: Full Body - a morning routine that gets you moving is the point, the stretch is the vehicle
Massage: Not primary
Also worth doing: A 10,000-lux light box for 20-30 minutes on waking from early autumn; keep a fixed wake time; get outside within an hour of waking; talk to a doctor if it is the same every year - preventive treatment before winter works better than treatment in it
What the evidence says: Bright light therapy is first-line with meta-analytic support; a randomized trial of 98 people found light and exercise each improved seasonal depressive symptoms and combined well, and network meta-analysis ranks exercise among the effective treatments. Outdoor morning exercise gives both at once.
The names above are the Targets qFIT tracks —
the Muscle Guide explains what each one does, and
Quick Add switches on the Exercises you
already have.
The qFIT routine for this
Ready-made routineStress & Anxiety Relief
qFIT already has this one built. It runs massage first, then stretching, then
strength — the order that works on a body that is already sore — and every
activity in it carries the reason it is there.
The button below opens your Checklist with this routine already selected, so instead
of your whole list you land on just its Categories, Targets
and Exercises, each with its checkbox, ready to tick as you work through
them.
Have more than one problem? Tick yours under My Problems on
My Profile and your Checklist's Routine list gains
Recommended for my problems — every routine for the problems you picked, merged
into one. Your picks stay private; that filter is the only thing they feed.
Get it checked if…
Thoughts of self-harm or hopelessness, or a low mood that does not lift in spring - see a doctor now, not next season
And whatever the body part: chest pain or unusual breathlessness on
exertion; a fever alongside the pain; unexplained weight loss; pain that is constant and
unrelated to how you move; new numbness, weakness or loss of bladder or bowel control; or
one calf that is swollen, warm and painful. Any of those, stop and get assessed.
How it usually goes
Bright light therapy works for most people with seasonal depression and typically shows effects within one to two weeks, which is fast compared with most treatments for mood. Starting in early autumn before symptoms establish works better than waiting. Exercise adds independently. If the pattern recurs every year, planning for it in September rather than reacting to it in December is the single most useful change. Severe or persistent depression, seasonal or not, deserves proper assessment.
Prevalence basis: AAFP seasonal affective disorder review; population surveys by latitude
Others the same routine covers
These share the Stress & Anxiety Relief routine, so the work is the same. If one of them also
sounds like you, that is a reason to expect more from it, not less.
This is general information, not a diagnosis, and it cannot examine you.
If it matches you, use it to ask better questions of a clinician rather than to replace one.