Many people feel down during the shorter, darker days of fall and winter, often called the “winter blues.” For some, those feelings are more serious. Seasonal affective disorder (SAD) is a type of depression that follows a seasonal pattern, with symptoms that last about 4 to 5 months a year, according to the National Institute of Mental Health (NIMH).

Symptoms of SAD can include fatigue, depression, hopelessness, and social withdrawal.

Light therapy, talk therapy, and antidepressant medicines are proven treatments for SAD. Researchers have also looked at whether folate affects mood.

Some, but not all, studies have linked lower folate levels to higher rates of depression, according to the NIH Office of Dietary Supplements. Scientists think this may be related to folate’s role in making brain chemicals that help regulate mood, but the connection isn’t fully understood.

For those taking antidepressants, some studies have found that low folate is linked to a poorer response to the medicine, and a few trials suggest folate may help as an add-on treatment, but the results are mixed. (https://www.ncbi.nlm.nih.gov/pubmed/15671130)

Making folic acid part of your daily routine is as easy as including some foods rich in folic acid into your diet. That includes dark leafy greens, beans, whole grains, oranges, sunflower seeds and lentils. Also, look for breads and cereals enriched with folic acid.

Of course, for those suffering from SAD, before doing anything else it’s important to visit with your physician.

Getting help

SAD is treatable. NIMH notes that treatments for SAD fall into four main categories that can be used alone or together, including light therapy, psychotherapy, and antidepressant medicines. Talk with your health care provider about what’s right for you. If you are in crisis, call or text 988 to reach the 988 Suicide & Crisis Lifeline.

Updated October 2026. This article is for general information and is not a substitute for advice from your health care provider.

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