How to Make the ‘SAD’ Diagnosis

’Tis the season for recognizing seasonal affective disorder (SAD). Just don’t expect to find SAD in diagnostic handbooks.

As a memorable term, SAD “stuck in the general public, and to some extent among health professionals,” said Scott Patten, MD, PhD, professor of psychiatry and epidemiology at the University of Calgary, Calgary, Alberta, Canada. “But it’s important to emphasize that that’s not an officially recognized diagnosis by the major classifications.”

Researchers coined the term SAD 40 years ago to describe a pattern of depression that sets in during the fall or winter and remits in the spring or summer.

Clinicians are diagnosing the disorder, albeit without that exact moniker.

In the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), the condition is considered a subtype of major depression.

So, for patients who meet criteria for recurrent major depressive disorder, the specifier “with seasonal pattern” might be applied.

The subtype covers cases where depressive episodes have followed a seasonal pattern for at least 2 years. Typically, onset occurs in the fall or winter followed by remission in the spring or summer. The opposite pattern is possible but less common.

When stressors such as seasonal unemployment better explain the pattern, the seasonal specifier should not be used, according to the manual. Bipolar disorder can follow a seasonal pattern as well.

Researchers estimate SAD affects about 5% of adults in the United States. The diagnosis is more common in women than in men, and more prevalent farther from the equator.

One Hallmark Symptom?

DSM-5 highlights characteristic features of winter depression, including:

• Loss of energy
• Hypersomnia
• Craving carbohydrates
• Overeating
• Weight gain

Kelly Rohan, PhD, a researcher at the University of Vermont, Burlington, Vermont, who has studied SAD since the 1990s, sees one symptom as a possible hallmark for the disorder: Fatigue.

“I’ve personally never met someone who met the full diagnostic criteria for the seasonal pattern that did not have fatigue as one of their symptoms,” Rohan said. “In theory, they could exist, but I have spoken to hundreds of people with seasonal depression, and I have never met them if, in fact, they do exist.”

That differs from nonseasonal depression, for which insomnia is a more common problem with sleep, Patten said.

Clinicians look for at least five symptoms of depression that cause substantial impairment and distress for at least 2 weeks, such as pervasive sadness, difficulty concentrating, low self-esteem, or loss of interest in hobbies.

An average episode of winter depression can last 5 months, however, Rohan said. “That’s a long time to be in a major depressive episode.”

Seeing Subsyndromal Cases

In people who do not meet criteria for major depression with a seasonal pattern, the change of seasons still can affect energy levels and mood. Some patients have “subsyndromal SAD” and may benefit from treatments that have been developed for SAD such as bright light therapy, said Paul Desan, MD, PhD, director of the Winter Depression Research Clinic at Yale School of Medicine in New Haven, Connecticut.

“Many people come to our clinic because they have seasonal changes that don’t meet the full criteria for depression, but nevertheless, they want help,” Desan said.

The 1984 paper that introduced the term SAD explored artificial bright light as a promising treatment for the condition. The researchers had heard from dozens of patients with “recurrent depressions that occur annually at the same time each year,” and bright light appeared to help alleviate their symptoms.

Subsequent trials have found the approach effective. Even in nonseasonal depression, bright light therapy may increase the likelihood of remission, a recent meta-analysis found. Light therapy also may bolster the effectiveness of antidepressant medication in nonseasonal major depressive disorder, a randomized trial has shown.

Other treatments for SAD include cognitive behavioral therapy (CBT) and bupropion XL, which is approved as a preventive medication. Other drugs for major depressive disorder may be used.

Quest for Biomarkers

To better understand SAD and how available treatments work, Rohan is conducting a study that examines potential biomarkers in patients treated with light therapy or CBT. She and her colleagues are examining circadian phase angle difference (how well internal clocks match daily routines) and post-illumination pupil response (how the pupil constricts after a light turns off). They also are measuring participants’ pupil responses and brain activity upon seeing words that are associated with winter or summer (like “blizzard,” “icy,” “sunshine,” and “picnics.”) 

Studies have shown treating patients to remission with CBT reduces the risk for recurrence in subsequent years, relative to other treatment approaches, Rohan said. That may be because CBT gives people tools to avoid slipping into another depressive episode, she said.

Avoid Self-Diagnosis

Rohan cautions patients against self-diagnosis and treatment.

“Having a conversation with your doctor is a good starting point,” she said. “Just because you can walk into Costco and walk out with a light box doesn’t mean that you should.” 

Light therapy can have side effects, including headaches, eye strain, and making patients feel wired, and it can be a challenge to determine the right dose, Rohan said.

Desan’s clinic website provides information about available devices for light therapy for patients who are looking to try this approach, but Desan agrees clinicians — especially primary care clinicians — can play a crucial role in helping patients. In more serious cases, a mental health expert may be necessary.

To start light therapy, Desan’s clinic typically recommends patients try 30 minutes of 10,000 lux bright light — roughly the brightness of being outside on a sunny day — before 8 AM for a 4-week trial.

Still, other specific issues might explain why a patient is struggling during winter months, Patten said. For example, people might experience financial stress around the holidays or consume excessive amounts of alcohol during that time.

“It’s important for clinicians to think broadly about it,” Patten said. “It might not always be light therapy or a medication. It might be focusing on some other aspect of what is going on for them in the winter.” 

Rohan’s research is funded by the National Institute of Mental Health, and she receives royalties for a manual on treating SAD with CBT. Patten and Desan had no relevant financial disclosures.