Navigating the Winter Blues: Understanding and Overcoming Seasonal Affective Disorder (SAD)

Seasonal affective disorder is depression that recurs in a seasonal pattern. Episodes arrive at about the same time each year and lift at about the same time, and for most people that means the darker months. The winter blues describes something milder: a dip in mood and energy that does not stop a person living their life.

The seasons in it are not fixed to particular months. South of the equator the dark stretch runs from June to August, and the diagnostic criteria are written around the time of year rather than the date. This page draws the line between a seasonal dip and a depressive episode, sets out what is known about the causes and what is not, and compares the treatments that carry evidence behind them.

Winter blues, or seasonal affective disorder?

Kaplan and Sadock's textbook describes winter SAD as a clinically significant level of depression, unlike the winter blues.² The line is not drawn by how low a person feels in a given week. It is drawn by whether whole depressive episodes recur season after season, and whether they interfere with work, study, relationships and looking after yourself.

The DSM-5-TR applies its seasonal pattern specifier to recurrent major depressive disorder, and requires two seasonal depressive episodes in the last 2 years with no nonseasonal episodes in that period.¹ Two further conditions sit with it: the episodes must lift at a characteristic time of year, and seasonal episodes must substantially outnumber nonseasonal ones over a lifetime. UK guidance puts the same idea in plainer words. The NHS sets the line at depression symptoms returning at a particular time of year for 2 years or longer.³

One exclusion matters and is often missed. The DSM-5-TR excludes patterns better explained by seasonally linked psychosocial stressors, such as seasonal unemployment or a school schedule, from the seasonal pattern specifier.¹ Someone whose mood drops every December because the work dries up and family pressure rises is describing something real, but it is not seasonal affective disorder.

What a clinician listens for in a first conversation:

• Whether the timing repeats, and how many years it has repeated.
• Whether the mood lifts at a predictable point, or simply drifts.
• What the person could not do this season that they could do six months earlier.
• Whether there have been spells of unusually high energy or little need for sleep.

That last question is not idle. Kaplan and Sadock's textbook records that SAD is diagnosed as major depressive disorder, bipolar I or bipolar II disorder, with the specifier with seasonal pattern.² The DSM-5-TR reports that among the bipolar disorders, a seasonal pattern is more likely in bipolar II than in bipolar I.¹ The seasonal shape on its own does not tell a clinician which of those they are looking at, and the answer changes the treatment.

Symptoms of a seasonal depressive episode

Winter-pattern episodes often look different from the picture most people hold of depression. The DSM-5-TR lists hypersomnia, overeating, weight gain and a craving for carbohydrates among the features often seen in seasonal major depressive episodes.¹ Kaplan and Sadock's textbook adds heightened sensitivity to interpersonal rejection and a leaden feeling in the extremities to the atypical features of winter SAD, with carbohydrate craving the most distinct.²

The core features of depression sit underneath: low mood through most of the day, loss of interest in what used to absorb you, poor concentration, and pulling away from people. Sleeping more and eating more is the part that surprises people, because depression is usually described as sleeping less and eating less. A seasonal episode can run the other way and still be a depressive episode.

Latitude, hemisphere and season

Most pages on this subject are written as though winter means December to February, which holds for roughly half the world.

The DSM-5-TR reports that the prevalence of the winter-type seasonal pattern varies with latitude, age and sex, and increases at higher latitudes.¹ The DSM-5-TR also reports that younger people are at higher risk for winter depressive episodes.¹ Distance from the equator is the variable, in either direction. Oslo and Ushuaia have more in common here than Oslo and Nairobi do.

Surveys reported in Kaplan and Sadock's textbook put the prevalence of winter SAD in the general population at between 4 and 9 percent. In those surveys women were up to four times as likely as men to be affected.² Kaplan and Sadock's textbook reports that as much as 20 percent of the population may have subsyndromal seasonal symptoms.² Those survey populations are not broken down by country in the source, so read the range as an order of magnitude rather than as a rate for where you live.

Winter is also not the only pattern. The DSM-5-TR notes that in most cases the episodes begin in fall or winter and remit in spring, and that recurrent summer depressive episodes are less common.¹ If the low period lands in January in Johannesburg, or in July in Toronto, that is worth telling a clinician rather than filing away as odd.

What causes SAD, and what is still unknown

The NHS says it is not known exactly what causes seasonal affective disorder, but that it is thought to be linked to reduced daylight in winter changing brain chemicals such as melatonin and serotonin.³ The National Institute of Mental Health explains that serotonin and melatonin help keep the body's daily rhythm tied to the seasonal night and day cycle. In people with SAD, those changes disrupt normal daily rhythms.⁴

The honest position is that the mechanism is not settled. Kaplan and Sadock's textbook reports that most individuals with SAD describe themselves as evening chronotypes, while nearly half do not have significantly delayed rhythms.² An account that fits half a population is not a full explanation. Inheritance plays a part: Kaplan and Sadock's textbook reports twin studies finding a heritability of 29 to 43 percent for seasonality or SAD.²

What a person thinks about the season is part of the picture too. The National Institute of Mental Health notes that negative thoughts about the winter or summer are common in people with SAD. It adds that it is unclear whether they are causes or effects, though they can be a useful focus of treatment.⁴ That uncertainty is worth keeping in view, because it is the point where talking therapy has something to work with.

What helps: light therapy, talking therapy and medication

The National Institute of Mental Health groups SAD treatments into light therapy, psychotherapy, antidepressant medication and vitamin D, and says there are no treatments specific to summer-pattern SAD.⁴ The NHS lists antidepressants, talking therapies such as cognitive behavioural therapy, and light therapy as treatments for seasonal affective disorder.³ The three are not equivalent in what they ask of a person or in what is known about them.

Light therapy

The National Institute of Mental Health says light therapy has been one of the mainstays of treatment for winter-pattern SAD since the 1980s.⁴ The specifics differ between authorities. The National Institute of Mental Health describes sitting in front of a very bright light box of 10,000 lux every day for about 30 to 45 minutes.⁴ Kaplan and Sadock's textbook describes a typical light therapy prescription as 45 to 90 minutes of daily exposure to an ultraviolet-filtered white light source of 5,000 to 10,000 lux for winter SAD.²

Timing is part of the prescription rather than a detail. Kaplan and Sadock's textbook reports that morning light therapy is most effective for the average patient with winter SAD, though evening light is also antidepressant for some.²

Two cautions come before buying any device. The NHS advises speaking to a doctor before trying light therapy for seasonal affective disorder, because it might not be suitable for people with certain eye conditions.³ The same seasonal pattern occurs in bipolar I and bipolar II disorder. Before adding daily bright light to a plan, a clinician needs the full mood history, including any spells of elevated mood.

How well it works is genuinely contested, and that is the part other pages leave out. Kaplan and Sadock's textbook calls light therapy the gold standard for winter SAD and reports that about half of individuals with SAD experience remission with it, while the mechanism is not yet clear.² The NHS says light therapy is not usually available on the NHS because there is not enough evidence to tell whether it is effective, while many people find it helps their symptoms.³ Both come from tier-one bodies, and quoting only one of them leaves out half of what is known. The device question is unsettled as well. Kaplan and Sadock's textbook notes that blue-wavelength light therapy appears as effective for SAD as brighter white light, but that the long-term safety of blue-enriched devices has not been established.²

Cognitive behavioural therapy

Kaplan and Sadock's textbook reports that CBT may be equally efficacious compared with light therapy for acute treatment of winter SAD, and may offer prophylactic benefit against recurrences in later years.² That second half is the practical difference between the two. A light box works while it is being used. A course of therapy works on the withdrawal and the conclusions a person has drawn about the months ahead, and the aim is that some of it holds into the next season.

In the room, your therapist will usually ask you to track what happens to your activity and your contact with other people as the season turns. You then work through together what you have come to expect of that time of year.

Antidepressant medication

Kaplan and Sadock's textbook states that multiple antidepressant medications have been used successfully to treat winter SAD.² Medication involves a longer commitment. Kaplan and Sadock's textbook sets the acute and continuation phase of antidepressant treatment for major depressive disorder at 8 to 12 weeks, with maintenance running 6 to 24 months or longer.² Your prescriber will review how you are doing rather than leaving you on a first choice, and will plan the maintenance stretch with you.

Managing the season yourself

Some of what helps is ordinary, and it works better started early rather than at the low point. Getting outside in daylight, even under cloud, keeps the strongest light source available in your day. A steady wake time supports a regular daily rhythm. Arranging to see people in advance beats deciding on the day, because the ability to decide on the day is often lost early in a depressive episode.

The limit is worth stating plainly. These steps support a mild seasonal dip and they do not treat a depressive episode. The NHS notes that many people need treatment every winter to stop symptoms from coming back.³ If your pattern is established, planning the season before it arrives, with a clinician, is a reasonable use of what you already know about your own year.

When to see a professional, and what assessment involves

The NHS says a GP will usually ask about your moods and how they change over time, and may ask you to fill in a questionnaire about your symptoms.³ A therapist or doctor assessing seasonal depression goes further than a single questionnaire. They will map the timing across years, ask what fell away in each episode, check for spells of elevated mood, and ask directly about thoughts of self-harm.

Reasonable points at which to take it to someone:

• The dip has returned in two or more years and lifts at roughly the same time.
• You are missing work or study, or withdrawing from people you would normally see.
• You are sleeping far more than usual and it is not helping.
• You have had thoughts of harming yourself, at any level of intensity.

Our guide on how to find the right therapist sets out what to look for and what to ask in a first call. If hopelessness is deepening, or you have thoughts of harming yourself, use the crisis resources at the top of this page now rather than waiting for an appointment.

Team TherapyRoute

References

1. [1] American Psychiatric Association (2022). Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision: Depressive Disorders. Held copy: APA - Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR, 2022). Pages cited: (pp 225-226).
2. [2] Sadock, Sadock and Ruiz (2017). Kaplan & Sadock's Comprehensive Textbook of Psychiatry, 10th edition. Held copy: Kaplan & Sadock's Comprehensive Textbook of Psychiatry, 10th ed (2017, vols 1+2). Pages cited: (pp 639-646), (pp 4299-4306).
3. [3] National Health Service. Seasonal affective disorder (SAD): overview. nhs.uk/mental-health/conditions/seasonal-affective-disorder-sad.
4. [4] National Institute of Mental Health. Seasonal affective disorder. nimh.nih.gov/health/publications/seasonal-affective-disorder.