In the late autumn and winter, some people develop symptoms of seasonal affective disorder (SAD), a type of depression with a recurring seasonal pattern.

Several types of treatment may be used to help people with SAD, including medications, cognitive behavioral therapy, and light therapy. Light therapy involves daily exposure to bright artificial light, typically for 20 to 60 minutes each morning, during the fall and winter months.

Several dietary supplements, including vitamin D, St. Johns wort, and melatonin, have been suggested as possible treatments for SAD, but its unclear whether any of them are helpful.