You may have heard of seasonal affective disorder (SAD) and associate it with the dark days of winter, but it turns out it can also be a problem during the summer months.

The Mayo Clinic explains, “SAD begins and ends at about the same times every year…. And [while] in most cases, seasonal affective disorder symptoms appear during late fall or early winter and go away during the days of spring and summer [some] people experience the opposite pattern. [They] have symptoms that begin in spring or summer.”

SAD affects about four to six percent of the U.S. population, but about 10 percent of sufferers get SAD symptoms during the summer season. The symptoms can consist of feelings of depression that happen daily or near-daily, a loss of interest in one-enjoyable activities, changes in weight or eating habits, low energy or changes in sleeping patterns, trouble concentrating, and more. Treatments differ, depending on the severity of symptoms.

It’s not clear what causes the condition, though it’s believed numerous factors can contribute, including a drop in melatonin and/or serotonin levels or a change in the body’s circadian rhythm.

If you think you might be suffering with SAD you should seek professional help.