When the days get shorter and the months get chillier, it’s hard not to feel your motivation and mood take a dip. For some, this sensation is fleeting, but for others the daylight decline can stir up something more serious known as Seasonal Affective Disorder (SAD).
“SAD is a type of recurrent major depressive disorder where symptoms emerge during a particular season — most commonly fall and winter when daylight decreases. It involves predictable, seasonal patterns of low mood and other depressive symptoms that remit when seasons change,” says School of Health and Behavioral Sciences Associate Director and Psychology Professor Joseph Trunzo, Ph.D.
While estimates vary by region and daylight exposure, Trunzo shares that approximately 1 to 2 percent of the United States' population experiences full SAD, and 10 to 20 percent experience a milder form often referred to as subsyndromal SAD or ‘winter blues.’
SAD symptoms are similar to that of depression but only occur in a seasonal pattern. These include persistent low mood, loss of interest or pleasure, decreased energy and/or increased fatigue, disruptions in sleep (too much or not enough), appetite changes (increase or decrease) and concurrent weight changes, difficulty concentrating, social withdrawal, and in severe cases, suicidality.
Below, Trunzo explains why people’s bodies react the way they do during the fall and winter months and the treatment options that exist for SAD:
A disruption to our circadian rhythm
People often feel low or sluggish during the darker months because of reduced sunlight, which disrupts individuals’ circadian rhythms (the body’s natural and internal processes that regulate sleep). On top of this, the body sees a decrease in serotonin activity, which affects mood stability, while melatonin production increases, which promotes sleepiness and can cause lethargy.
“Since SAD often occurs in colder months, people are also engaging in less outdoor activity, reduced social interaction, and lower physical activity — all of which can affect mood,” Trunzo says.
The difference between the winter blues and clinical SAD, Trunzo notes, is that winter blues are less persistent and severe.
“Everyone has bad days and maybe even a few of them in a row, especially during winter; however, when you have significant symptoms that interfere with your ability to function and that are persistent for at least two seasonal cycles, this is more likely full SAD,” he says, adding that the disorder is highly recurrent and is likely to persist through successive seasons.
SAD rates also tend to increase at higher latitudes where daylight is more limited and is diagnosed more frequently in women, though men often experience more severe symptoms when affected. Trunzo shares that anyone with a history of depression themselves or in their family is also at increased risk.
Testing treatment options
If left untreated, SAD — just like any ignored illness — runs the risk of becoming more severe, chronic, and could negatively impact an individual’s ability to function. Untreated symptoms could devolve into more severe depression, social isolation, declines in academic or occupational performance, increased substance use as a coping strategy, heightened risk of suicidal thoughts in severe cases, or recurrent, worsening seasonal episodes over time.
When getting help, Trunzo explains that the first-line treatment of choice is bright light therapy, which involves using a 10,000-lux light box for 20 to 30 minutes daily in the morning.
“I know it seems silly, but it actually works well for most people. It helps regulate circadian rhythms and serotonin function,” he says, noting that you don’t have to buy a fancy expensive one; you could also purchase a grow light at a hardware store since this will do the same thing as long as it’s in the correct lux range.
He adds that cognitive behavioral therapy, anti-depressant medication (mostly selective serotonin re-uptake inhibitors like Prozac, Zoloft, or Bupropion XL), and lifestyle changes (increased outdoor activity, exercise, regulating sleep, vitamin D supplementation) have also been shown to be effective.
“I often recommend a combination of some or all of these approaches to improve effectiveness and outcomes,” Trunzo says.
Since light exposure is already the gold standard of treatment, SAD research is focusing more on timing, intensity, and delivery of light exposure.
“Innovation in circadian rhythm-based interventions, wearable light devices, and specific CBT digital therapeutics protocols hold promise,” Trunzo says.