In his memoir, A Moveable Feast, the author Ernest Hemingway reflects on the sadness of the winter season:

“You expected to be sad in the fall. Part of you died each year when the leaves fell from the trees and their branches were bare against the wind and the cold, wintery light. But you knew there would always be the spring, as you knew the river would flow again after it was frozen.”

Though seasonal affective disorder (SAD) would not be named for another 20 years, Hemingway describes winter depression in a fashion that all but predicts the criteria that would be found in the Diagnostic and Statistical Manual of Mental Disorders (DSM). SAD is a depressive disorder with episodes occurring in a seasonal pattern.

It is estimated that SAD affects anywhere from 1% to 6% of people in the United States, with increasing prevalence in higher latitudes. Studies have found a higher incidence of SAD in women, especially in childbearing years, with a female-to-male ratio of about four to one (Kurlansik SL & Ibay AD, Am Fam Physician 2012;86(11):1037–1041). SAD has also been found to be more common in younger people and those who have a first-degree relative with depression.

Understanding SAD

Though SAD is largely differentiated from other mood disorders by seasonality, certain symptoms also set it apart. Winter depressive episode symptoms, including hypersomnia, increased appetite, carb-craving, decreased energy, and weight gain, are consistent with atypical depression. Rarer spring-onset depressive episodes tend to reflect more typical depressive symptoms, including insomnia, decreased appetite, and poor energy.

In terms of pathophysiology, SAD is not entirely understood. The phase shift hypothesis, based on circadian phase advance or delay, is a favored theory in the scientific literature. The hypothesis asserts that decreased light exposure and altered sleep-wake cycles affect internal circadian rhythms and melatonin release, resulting in depressed mood.

Retinal sensitivity to light, abnormal melatonin metabolism, genetic variations affecting circadian rhythm, and neurotransmitter dysfunction may predispose people to SAD. Serotonin, specifically, is thought to be implicated, with some studies showing a decrease in central serotonergic activity in patients with SAD.

Treatments for SAD

Treatment options that have been studied and found appropriate for SAD include pharmacotherapy, cognitive behavioral therapy (CBT), and light therapy (LT). No one treatment has been found to be superior consistently.

Pharmacotherapy. Several studies have demonstrated the efficacy of selective serotonin reuptake inhibitors (SSRIs) for SAD. However, many early studies were limited by small study size or short treatment length. A 2004 study examined 187 patients with seasonal pattern, recurrent winter depression who were treated for eight weeks with placebo or sertraline (Zoloft) in flexible dosing (50–200 mg). Treatment with sertraline resulted in a significantly greater response, suggesting that, with appropriate length of treatment and optimal dosing, SSRIs are an effective treatment for SAD.

CBT. CBT can also be tailored to treat SAD, though data are limited. Therapy can be structured to address the role of the seasonal environment and to develop wintertime coping strategies. According to SAD-focused CBT designed by psychologist Kelly Rohan, negative thoughts about weather and decreased daylight can be used as focal points for cognitive restructuring, and interventions, such as wintertime hobbies, can serve as a means of behavioral activation. Patients should also develop an awareness of warning signs (Rohan KJ, Medscape Multispecialty; http://bit.ly/18auw1q).

Light Therapy (LT). Light therapy poses a unique treatment for SAD and may be preferable for some patients who don’t want to or can’t take medication. Light boxes may be less expensive than medication long-term, depending on insurance and medication choice.

Accepted LT guidelines (Kurlansik SL and Ibay AD, op.cit) call for the following:

1. Position the patient about 12 to 18 inches from a source of 10,000 lux of white, fluorescent light without ultraviolet wavelengths.


2. Have therapy last for 30 minutes daily in the early morning. [See “This Month’s Expert” for a discussion on the importance of considering the “biological morning” rather than the “morning outdoors.”]


3. Patient must keep eyes open, although it is not necessary to stare at the light.


4. In subsequent years, begin treatment in early autumn to avoid relapse.

Multiple studies have been performed studying LT, comparing it to placebo or treatments such as antidepressants and CBT. The Can-SAD study randomly assigned 96 patients with MDD with seasonal pattern to either 10,000-lux LT and placebo or 100-lux LT (placebo) and fluoxetine (Prozac) 20 mg daily. Both groups responded well to treatment, but there was no difference in clinical response rates. However, patients receiving LT responded more quickly and complained of fewer side effects (Lam RW et al, Am J Psychiatry 2006;163(5):805–812).

Research has compared CBT, LT, and combination treatment. One study randomized 61 patients with MDD recurrent with seasonal pattern to six weeks of SAD-tailored CBT, LT, a combination of the two, or a control group. All three treatment groups responded, but combination treatment resulted in a higher remission rate than LT alone (Rohan KJ et al, J Consult Clin Psychol 2007;75(3):489–500).

Another study examined outcomes from the first study one year after treatment and found that the CBT and combination treatment groups had lower rates of recurrence of winter depression compared to the group receiving only LT (Rohan KJ et al, Behav Ther 2009;40(3):225–238).

Other suggested treatments for SAD include exercise, dietary modification, mindfulness, winter travel, or relocation to warmer climates. Given the recurrent nature of the illness, psychoeducation and preventative treatment may be especially valuable.

How DSM-5 Defines SAD

SAD first appeared in DSM-III-R as a modifier for recurrent mood disorders. It remains a modifier, “with seasonal pattern,” in the newly-published DSM-5 released in May 2013 (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. Arlington, VA: American Psychiatric Association; 2013). Although there were no significant changes to the diagnostic criteria in the new manual, the specifier now appears in both “Depressive Disorders” and “Bipolar and Related Disorders.” To be given this specification, an individual must also meet the criteria for one of three types of disorders: recurrent major depressive disorder (MDD), bipolar I disorder, or bipolar II disorder.

In addition to meeting mood disorder criteria, the disease course must also fit the following criteria as outlined in DSM-5:

• There must be a “regular temporal relationship” between the onset of major depressive episodes and a particular time of the year (eg, the episodes regularly appear in the fall or winter). However, clinicians are cautioned not to include cases in which the depression is caused by seasonally-related psychosocial stressors such as regularly being unemployed each winter.


• Full remissions (or a change from major depression to mania or hypomania) occur at a characteristic time of the year, such as the patient’s depression resolving in the spring.


• In the past two years, two major depressive episodes occurred that demonstrate the temporal, seasonal relationships as defined in the above criteria and no non-seasonal major depressive episodes occurred.


• Seasonal major depressive episodes substantially outnumber the non-seasonal episodes over the individual’s lifetime.

DSM-5 also notes that there only has to be a regular seasonal pattern of one type of episode (ie, mania, hypomania, or depression) and any other types need not follow a seasonal pattern. The mood episodes usually have onset in fall-winter and remit in spring-summer, though some individuals experience onset in warm seasons. It is not known whether seasonal pattern is more common in MDD or bipolar disorder, but of those with bipolar, more have bipolar II than bipolar I (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, op.cit).

TCRBH’s Take: There is still much to be learned about SAD and its treatment. Diagnostic challenges include distinguishing seasonal mood changes from changes that are associated with life events that coincide with certain times of the year. In terms of treatment, light therapy can be an appealing, non-drug option and it is important for the clinician to work with the patient to determine when its use (eg, both in terms of start date and time of morning) is most beneficial.