We’re heading into a second Pacific Northwest winter under the cloud of a pandemic, which is a perfect recipe for feeling a little blue. For some people, however, the “winter blues” go beyond feeling a bit blah because the skies are gray and it starts getting dark in the afternoon — they have seasonal affective disorder, or (appropriately) SAD.

SAD is a biological and mood disorder with symptoms typically beginning in late fall or early winter. Symptoms get progressively worse until they start to fade in spring or summer. SAD-specific symptoms are oversleeping, overeating and social withdrawal, but because SAD is a type of major depressive disorder, symptoms may also include depressed mood, loss of interest in usual activities, low energy, feelings of hopelessness and trouble concentrating. As with major depression, some people with SAD may experience suicidal thoughts. Even though its seasonality sets it apart from major depression, SAD affects up to 5% of the U.S. population for an average of almost five months each year, which means it’s considered a major mental health disorder that affects daily quality of life.

Unfortunately, it’s not entirely clear what causes SAD. Some research suggests that people with SAD may have disrupted levels of serotonin (a brain chemical that regulates mood) and melatonin (a hormone that helps maintain the normal sleep-wake cycle). These disruptions would make it hard to adjust to seasonal changes in day length, explaining why SAD is more common and more severe in areas where the sun rises the latest and sets the earliest in winter — areas like the Northwest.

OK, so SAD sucks. Can nutrition help? Unfortunately, while it’s tempting to try a “food as medicine” approach for managing SAD symptoms — a quick search online may leave you convinced that vitamins D and B12 will cure what ails you — the research is less compelling. While low levels of vitamin D have been associated with an increased risk of depression, a 2020 systematic review pointed to a study that randomly assigned participants to take either a high dose of vitamin D or a placebo for 12 weeks during the winter and found no significant differences between groups. A study looking at the effects of supplemental vitamin B12 had similarly underwhelming results.

When I had SAD for a few winters in the early 1990s — the early days of SAD awareness — the conventional wisdom was that SAD sufferers should eat a high-carbohydrate diet to boost serotonin levels. However, that 2020 systematic review also reported that while people with SAD have increased cravings for carbohydrate-rich foods, evidence from randomized controlled trials concluded that eating more carbs doesn’t help symptoms.

The bottom line is that trying to use nutrition to reduce SAD symptoms could be harmful if what you really need is mental health support. There’s a shortage of high-quality research on the role of nutrition in managing SAD, in part because of uncertainty about the precise underlying causes. So, as with any physical or mental health condition, the goal should be managing symptoms with treatments that have a proven track record.

According to the National Institute of Mental Health, one of those treatments is light therapy — sitting in front of a special bright light box for 30-45 minutes a day — to make up for some of winter’s missing sunlight. Psychotherapy and antidepressant medications are other treatments that may be effective. While good nutrition never hurts — it supports body and mind as you follow established SAD treatments — it’s not a stand-alone option.