With short days, cold weather, and limited opportunities for outdoor recreation, many people find themselves suddenly—and understandably—feeling low in late fall and winter. For some people, this is simply a shift in mood that lifts as soon as those first blossoms appear in early spring, while for others, it may be a sign of a diagnosable, but potentially treatable, mental health issue.

According to a review published in Progress in Neurology and Psychiatry, Seasonal Affective Disorder (SAD) affects approximately five percent of the population. However, countless people may experience similar symptoms, often colloquially known as “winter blues,” without necessarily receiving a clinical diagnosis.

Read on to discover what doctors and mental health professionals say is the major difference between SAD and winter blues and what you can do if you think you may be affected. And if you want to improve your wellbeing fast, check out The One Vitamin Doctors Are Urging Everyone to Take Right Now.