– This time of year, that blaring alarm clock might bother you a little more. It’s cold and dark outside, and your commute feels longer than usual too.

When you finally get to work, you might find yourself more annoyed than usual by a co-worker chewing an apple too loudly, and you slump in your seat with a sigh.

Many workers experience the “winter blues,” but it’s not the same thing as seasonal affective disorder (SAD), which is a form of depression the American Psychological Association classifies as a serious medical condition related to changes in the seasons — and shortage of sunlight.

“This is a real diagnosis, and it’s recognized by psychiatrists in many countries,” said Norman Rosenthal, clinical professor of psychiatry at Georgetown University School of Medicine. Rosenthal gave the disorder its name.

According to the APA, symptoms of SAD include fatigue, pervasively sad mood, loss of interest, sleep difficulty or excessive sleeping, craving and eating more starches and sweets, weight gain, feelings of hopelessness or despair, and thoughts of suicide. In 2008, Rosenthal wrote in a journal article on seasonal affective disorder that 6 percent of the U.S. population is affected.

The Society of Human Resource Management says those symptoms could individually or collectively affect employee productivity by reducing morale and increasing absenteeism, mistakes, and safety risks in environments like manufacturing or construction.

“You may not see anything on the surface, but people who are unevenly productive across the year, it’s in the interest of management to give them the light they need to be as productive as they can be. It’s not in their interest to deny it,” Rosenthal said.

SAD has been the subject of a workplace legal controversy concerning access to light.

In 2010, Renae Ekstrand, a former teacher at the Somerset school district in Wisconsin, won a case against her former employer for failing to address her needs as someone with SAD, which is recognized under disability law.

Ekstrand joined the Somerset district in 2000 after teaching for 10 years and was assigned to a room with no windows in 2005. After her request to change to an available classroom with an exterior window to accommodate her SAD was denied by the district, Ekstrand began having symptoms like fatigue, trouble organizing tasks and anxiety. She went on medical leave that October.

Employers have recently been more forthcoming about how they accommodate workers with SAD, said Linda Batiste, principal consultant at the Job Accommodation Network, which is part of the U.S. Department of Labor’s Office of Disability Employment Policy.

“It does look like employers are saying, ‘Let’s just go ahead and provide them with what they need,’ ” Batiste said. “It’s a lot easier than arguing in court, especially for something like a light box.”

SAD can also be treated with antidepressant medication.

Rosenthal stressed the importance of light therapy, whether through sitting near a window at work, trimming shrubbery that is blocking light at home, or getting a light box on your desk.

“Light therapy still works … and one thing that is new is that there is even more research that it doesn’t have to be seasonal for us to benefit from it,” he said.