For some, the color of Christmas is not red and green but blue.

"Even people who ordinarily aren't depressed may have bouts of depression around Christmas," said Glenview resident Ralph Erber, an associate professor of psychology at DePaul University who has conducted research on mood management.

"When workplaces and malls shut down for the holidays, the lack of activity can cause some people to ruminate on losses or things they haven't done," he said. "Problems tend to be magnified."

Symptoms of Christmas depression may include restlessness and sleeplessness, changes in appetite, thoughts and conversations that dwell on failure, and a general sense of dread, he said.

For those who are feeling down but are not clinically depressed, keeping busy is a good way to stay in good spirits during the holidays, Erber said.

"Do something you enjoy but haven't done in a long time," Erber suggested. "Choose something that keeps you occupied, something with a goal structure." For example, Erber said that each Christmas he shines up and assembles a miniature railroad.

"Plan lots of activities with family and friends," Erber said. "It prevents you from ruminating about bad things."

Reporter's note: Erber is available for interviews at his office: 773-325-4256 or home 847-832-9448