When crisp fall days give way to cold winter weather, for some people, the change can trigger seasonal affective disorder (SAD), a type of depression that saps their energy and destabilizes their mood. “People with SAD typically present with symptoms that include overeating, weight gain, oversleeping, lethargy and fatigue, and significant cravings for sugary or starchy foods,” says Elizabeth Waterman, PsyD, a psychologist at Morningside Recovery Center in Newport Beach, California. “Symptoms are worse in the evening and typically last for five months.”

What causes SAD isn’t known, but during the shorter days of winter, the body may produce the hormone melatonin either earlier or later in the day than usual. These changes can lead to SAD symptoms.

Currently, the most effective treatment for SAD is cognitive behavioral therapy. CBT helps depressed people examine and restructure their negative thinking patterns and the behaviors that perpetuate depression. Another successful treatment for SAD is called phototherapy. The treatment entails patients “sunning” themselves with a light box for 60 to 90 minutes each morning. But sunshine can also work wonders. “Studies show improvement in SAD symptoms when people walk outside for at least one hour each day,” Waterman says.

Still, some people might prefer to take a pill rather than sit in front of a light box. For them, antidepressants called selective serotonin reuptake inhibitors (SSRIs) offer another option. Just let science light the way!