By Carina Storrs
An estimated 5 percent of Americans experience seasonal affective disorder (SAD) a type of depression that sets in during the shorter days of fall and winter and lasts until spring.
SAD is triggered by the reduced number of daylight hours during the winter months, although other factors, such as cold temperatures and weak daylight, can make symptoms worse. "The way we diagnose SAD is to diagnose depression that follows a seasonal pattern, says Kelly Rohan, PhD, professor of psychological science at the University of Vermont, Burlington. "Many of the symptoms of SAD are the same as those of clinical, or major, depression—low mood, loss of interest in enjoyable activities, fatigue." But there are a few differences between SAD and major depression.
The difference between SAD and major depression
People with SAD often sleep and eat more, possibly gaining weight as a result, unlike people with major depression who tend to have difficulty sleeping and don't have much appetite. It is also less common for people with SAD to think about suicide. "I think it is because there is a light at the end of the tunnel," says Rohan. "People know that spring is coming, [and] they're going to feel better eventually," says Rohan.
Who is at risk for SAD?
In addition to people who live closer to either the north or south poles, those at higher risk of SAD include women, people in their early 20s, people with a family history of SAD, and those who also have major depression or bipolar disorder. Some research suggests that women who have depression during pregnancy could experience worse depressive symptoms during winter months.
Pregnancy and SAD
A small study of 19 pregnant women with depression found that those assessed on days when there was less daylight (like winter days) had severe symptoms, while those assessed on a long summer day had only mild symptoms. In contrast, among a dozen women who did not have depression during pregnancy, there was no increase in depressive symptoms during winter months. Though more research is needed, "the paper is meant to alert people who treat women with depression during pregnancy that seasonal effects are also playing a role in the severity of that depression," says Charles Meliska, PhD, lead author of the study and a project scientist in the department of psychiatry at the University of California, San Diego.
But for women who are not already experiencing prenatal depression, research does not suggest that pregnancy is a risk factor for developing SAD, Meliska adds. "Pregnancy can trigger depression," says Rohan, "but I can't really imagine a scenario that would create season-specific depression." However, Rohan agrees that if "someone already has SAD, pregnancy might make it worse."
Is there a connection between SAD and PPD?
It is unclear whether winter months could increase the risk or severity of depression after a woman has delivered. Although several small studies found higher rates of postpartum depression (PPD) among women who gave birth in the winter, a large study of women in different parts of the United States did not find a link between PPD and season of birth.
If you are experiencing symptoms of depression during pregnancy, it is important to let your healthcare provider know. She can screen you for depression to determine if seeing a mental health professional could help you feel better.
What causes SAD?
Though it seems intuitive that darker days might lead to darker moods, the cause of SAD is not well understood. Most experts believe it results from changes in the timing of the production of melatonin, a hormone produced at night that signals to your body it is time to sleep, Rohan says. According to this hypothesis, people continue making melatonin later on winter mornings because dawn comes later, making them feel tired and groggy when they are supposed to be waking up. In a smaller subset of people with SAD, the early evenings could spur their bodies to make melatonin earlier, and they are "falling on their face with fatigue" in the early evening, Rohan says. Along with fatigue, people can have other symptoms of depression, like a low mood.
How is SAD treated?
The first-line treatment for SAD is light therapy, which involves sitting in front of a special source of bright light for between 30 minutes and two hours, shortly after waking up. (Light boxes used to treat SAD filter out most or all ultraviolet rays.) For people who have a slump in the evening, a quick session in front of a light box at dusk could also help. The idea is that the light box "should turn off that melatonin production and shift the rhythm back into the normal position, like it would be in the summer," Rohan says.
Meliska notes he is cautious about prescribing light therapy for people with bipolar depression because it can lead to manic symptoms.
Although most patients with SAD get some relief from light therapy, a recent study by Rohan and her colleagues suggested that cognitive behavioral therapy (CBT) could have a more lasting benefit. Among 177 participants in the study, 89 were given a light box for six weeks, and another 88 received six weeks of CBT to learn new ways of thinking and acting during winter. The two groups had similar rates of recurrence the next winter, but by the second winter after the treatment, only 27 percent of the CBT group had another bout of SAD, compared with 46 percent of the light therapy group.
There is no reason that pregnant women who are experiencing seasonal depression wouldn't be eligible for light therapy or CBT, Rohan says. However, she notes that postpartum women who are breastfeeding should not breastfeed in front of the light box because the bright light could hurt a newborn's eyes.
Melatonin pills are another potential treatment option for SAD. "We are experimenting with oral melatonin, and the reason is because we and others have discovered it acts in the opposite way as light in shifting the 24-hour body clock," says Alfred J. Lewy, MD, PhD, and psychiatrist at Oregon Health & Science University in Portland. Instead of (or in addition to) light box therapy in the morning, a patient could take a melatonin pill in the late afternoon, Lewy says. Alternatively, a few people with SAD do best with getting exposure to bright light in the evening and taking low-dose melatonin in the morning. Some patients prefer taking melatonin because it is more convenient than sitting in front of a light box, Lewy says.
But the treatment is still considered experimental, so people have to buy the over-the-counter pills intended to be taken right at bedtime to make you sleepy. To get a lower dose and minimize drowsiness, they need to be cut into about tenths, he says. He also cautions that people who still get sleepy on low-dose pills should not take melatonin during the day.
Although melatonin pills are available over the counter, always talk to your healthcare provider before taking them to treat SAD, especially during pregnancy. Although there is no research indicating that melatonin is harmful, there is also no evidence that the supplement is safe. Work closely with your provider to come up with the treatment that is best for you.
“The good news here is that for the most part depression associated with SAD is treatable,” says Seleni clinical director, Christiane Manzella, PhD. “But with any emerging depression or prior depression that intensifies or interferes with your ability to function, or if you just do not feel like yourself, reach out for help from a qualified mental health professional. And seek immediate help if you have thoughts of hurting yourself.”