Seasonal affective disorder (SAD) affects over 10 million people in the US


This Sunday, November 3, most of America will be traveling back in time – by an hour.

That’s when daylight saving time ends and we set back our clocks, signaling the transition into late fall and winter.

With this changing of the clocks, daylight ends earlier.

When this happens, some people may experience emerging feelings of sadness and sluggishness, and fluctuations in weight.

If you suffer from these symptoms, you may have seasonal affective disorder (SAD), a type of depression related to changes in the seasons.

SAD affects an estimated 10 million Americans, with women four times more likely to be diagnosed with it than men. Fortunately, there are treatments available that have proven effective in treating the disorder.

How does one distinguish between SAD and ordinary sadness?

What are the possible treatments? And what do scientists know about the underlying causes of the disorder?

For answers to some of those questions, BU Today talked to Sanford Auerbach, a School of Medicine associate professor of neurology and psychiatry and director of the Sleep Disorders Center at Boston Medical Center.

What is seasonal affective disorder (SAD)?

SAD refers to changes in mood that occur when symptoms fluctuate according to the season of the year. Most commonly, it refers to depression associated with the winter months, typically fall and winter.

It’s thought to be related to the fact that during the winter months we have shorter days.

What are the symptoms?

Typically they are associated with mood changes—depression, for instance. People who suffer from SAD may find that they have difficulty waking up in the morning, that they have less energy, that they have an increased appetite.

It may be more difficult for them to concentrate. Maybe they have less motivation to do things.

The flip side of it is that the opposite happens in the shorter months, like spring and early summer, where people will perhaps sleep a little less, are maybe more energetic, maybe more active, maybe even in some cases a little more “hypomanic,” a little on the manic side.

From a technical perspective, it’s not just a matter of being depressed in the winter months. It’s also being manic, if you will, in the longer days. So basically, it’s a disorder of mood that seems to be linked to the seasons.

How do you recognize that you are suffering from SAD and not something else?

That’s tricky, because although people have latched onto the fact that in a lot of cases it’s related to the light cycle, there are also a lot of other things that go on—work changes, holidays, colder weather—that may be more stressful for some people than others. So there are many factors.

The way you recognize it is that over the course of several years, you see that there’s a recurrent theme: every four months, you start to have these changes in mood. So after this happens maybe three years or more, then you could consider that it’s SAD.

How many people suffer from SAD? Are certain individuals more at risk than others?

When you look at temperate climates, I think it’s estimated that 5 percent of the population may have this.

Certainly for people who live in areas where you don’t see such great variation in seasons, it’s not as likely to occur. The extreme would be people who live in equatorial areas. There, the times don’t shift much.

They have close to 12-hour days all year round. Whereas people farther north or farther south can have very long days in the summer but very short, or nonexistent, days in the winter.

What are the treatment options for people with SAD?

There are a couple of options here. One is to use some sort of light therapy. You can get easily available light boxes. Usually the prescription is to be exposed to 10,000 lux.

One lux is one candle-foot power – the amount of light that you get if you’re one foot away from one candle.

Usually they’re full-spectrum lights, and usually the intensity varies according to how far it is from you. You want to sit in front of it in the morning for about 30 minutes each day. Morning exposure tends to be much more powerful than exposure in the evening or the middle of the day.

The other option is to treat it like depression. A lot of things that have been shown to be effective for depression are effective for SAD, like the usual sort of antidepressants.

Are there ways to prevent SAD or mitigate its symptoms?

Start treating it before it happens. Or, in the winter, move down to South America.

What do doctors and scientists still not know about SAD?

I think that figuring out what it is about the light that these cells in the back of the eye particularly implicated in this, needs to be studied a bit more. And some of those pathways are being studied more.

People who suffer from SAD may find that they have difficulty waking up in the morning, that they have less energy, that they have an increased appetite. It may be more difficult for them to concentrate. Maybe they have less motivation to do things.

People are also trying to figure out, is it the light intensity?

A few people have adjusted light gradually, like a sunrise—is that more effective or less effective?

What about the genetics of it?

How can you predict who’s at a greater risk than others for this? One of the troubles of the light therapy is it varies a little bit from person to person, from researcher to researcher.

The idea is to sit in front of the light for 30 to 60 minutes, but that requires some lifestyle changes and a time commitment.

What do you hope for in the near future regarding SAD research?

I think it’s important to appreciate the impact of light on mood, but also cognition. They are very closely related because cognition does fluctuate with mood.

What is the effect of these seasonal affective disorders on things like memory and cognition in general?

Is it better to take your harder courses in the fall semester or the spring semester?

Seasonal affective disorder (SAD) is a seasonally recurrent type of major depression that has detrimental effects on patients’ lives during winter. Little is known about how it affects patients during summer and about patients’ and physicians’ perspectives on preventive SAD treatment.

The aim of our study was to explore how SAD patients experience summers, what type of preventive treatment patients implement, which preventive treatment methods, if any, physicians recommend, and what factors facilitate or hinder implementation/recommendation of SAD prevention.


We conducted 15 semi-structured interviews, ten with adult patients with a history of SAD and five with physicians. Transcripts were analyzed by two researchers using an inductive thematic analysis approach.


One group of patients was able to enjoy summer and ignore thoughts of the upcoming winter. The other group feared the impending depressive episode in winter, and this fear negatively impacted these patients’ well-being during the summer.

Preventive treatment was a relevant issue for all patients, and all but one person implemented SAD prevention during summer. We identified six factors that influenced patient use of preventive treatment of SAD.

Four factors occur on an individual level (knowledge about disease and preventive treatment options, experience with treatment in acute phase, acceptability of intervention, willingness to take responsibility for oneself), one on an interpersonal level (social and work environment), and one on a structural level (healthcare system).

All psychiatrists recommended some kind of preventive intervention, most commonly, lifestyle changes. Four factors influenced psychiatrists in recommending prevention of SAD (patient expectations, disease history and stability, risk/benefit ratio, lack of evidence).


Success in the implementation of SAD prevention does not solely depend on the willingness of the patients, but is also influenced by external factors. Raising awareness of SAD among general practitioners and low-level access to mental-health support could help patients find appropriate help sooner. To better guide the optimal treatment choice, comparative effectiveness research on treatments to prevent a new onset in patients with a history of SAD and clinical practice guidelines on SAD are needed.


Seasonal affective disorder (SAD) is a subtype of major depression that affects 2–8% of the total population in Europe [15]. It usually begins in fall/winter and remits in spring [68]. SAD is characterized by a high degree of persistence only resolving completely in one out of five patients after five to eleven years. In 22–42% of those affected, it persists with the seasonal pattern, and in 33–44% SAD turns into a non-seasonal major depression [910].

Depressive episodes negatively impact patients’ social as well as working lives [1112]. In addition to depressive symptoms, most patients also experience hypersomnia, increased appetite often accompanied by weight gain, and extreme fatigue during winter months [13].

In summer, SAD patients are free of depressive symptoms. However, little is known whether or not the fear of upcoming depressive episodes impacts their well-being.

Light therapy is the first-choice treatment for acute SAD episodes and second-generation antidepressants are the second-choice treatment [1416]. Other treatment options comprise agomelatine, melatonin, cognitive behavioral therapy, or lifestyle and diet changes [1723].

The predictability of new depressive episodes in SAD patients provides a rationale for using these treatments preventively [24], beginning either in symptom-free summers or in fall when patients realize the first mild symptoms.

A third approach to avoid the onset of a full-blown depression in the upcoming winter season is to continue acute treatment during summer.

Little guidance on the prevention of SAD exists. A German clinical practice guideline recommends starting light therapy in times of risk [25], while other guidelines do not provide specific recommendations for prevention of SAD [2627]. Also, the evidence on efficacy and safety of preventive treatment in SAD patients is limited.

A systematic review demonstrated that the preventive use of the antidepressant bupropion extended release (XL) reduced the number of patients developing a new depressive episode in the next winter by 44% compared to placebo [placebo: 27% vs. bupropion XL; 15%] [28].

A randomized controlled trial on psychotherapy showed that cognitive behavioral therapy led to 27% recurrence of SAD episodes in the following winters compared to 46% with light therapy [29].

A pilot study in 46 SAD patients, however, showed that preventive mindfulness-based cognitive therapy did not prevent recurrence of SAD better than “treatment as usual” when administered in a symptom-free time [30]. No evidence on preventive efficacy of other antidepressants [28] or other types of psychotherapy exists [31].

Systematic reviews on preventive light therapy [32], on agomelatine, and melatonin [33] were not able to draw valid conclusions on efficacy and safety of these preventive treatments either. Nevertheless, preventive treatment is common in clinical practice. A recent survey in German-speaking countries demonstrated that 81 out of 100 interviewed hospitals recommend preventive interventions to their SAD patients, most frequently, lifestyle changes and antidepressants, followed by psychotherapy and light therapy [34].

When evidence from clinical studies is scarce and guidance from clinical practice guidelines is unavailable, treatment choice should be heavily based on patient preferences and the clinical expertise of physicians. To our knowledge, no study has yet qualitatively explored patients’ and physicians’ perspectives on prevention of SAD.

The aims of our study were to investigate how patients with a history of winter-type SAD experience summers, what type of preventive treatments they implement, if any, and what facilitates or hinders the implementation of preventive treatment in symptom-free periods. In addition, we strove to identify factors that influence physicians in prescribing preventive treatment to SAD patients.

Boston University
Media Contacts:
Madeleine O’Keefe – Boston University
Image Source:
The image is in the public domain.


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