FRIDAY, Dec. 17 (HealthDay News) Christmas and other winter holidays are supposed to be a happy time of year, which makes it all the more stressful when they are anything but joyous.

This is the time of the year when people are especially vulnerable to depression, Dr. Angelos Halaris, a psychiatrist with the Loyola University Health System, said in a university news release. Shopping and entertaining can be stressful, while reflecting on lost loved ones can renew feelings of grief. Add to that the turmoil caused by the poor economy. All these things can help depression gain a foothold in certain individuals.

What to do? If you're feeling extremely depressed and unable to function, consult a mental health professional immediately. Danger signs include two or more weeks of mood problems, crying jags, changes in appetite and energy levels, overwhelming shame or guilt, loss of interest in daily activities, difficulty concentrating and grim thoughts about death or suicide.

If you feel like your symptoms aren't severe but still make you miserable, Halaris has these suggestions:

"Exercise works. Having replenishing relationships matter. Doing things that you find rewarding and fulfilling is helpful, as is attending religious services," Halaris said in the news release. "Getting plenty of sleep and taking care of yourself works. We all have our limits, and learning to live within those limits is important."

Be aware that depression, exhaustion and lack of interest in life could be a sign of seasonal affective disorder, caused by the lack of sunlight. One frequent symptom is a desire for sweets.

"The most common type of this mood disorder occurs during the winter months," Halaris said. "SAD is thought to be related to a chemical imbalance in the brain, brought on by lack of light due to winters shorter days and typically overcast skies."

What can you do about SAD? "If at all possible, get outside during winter, even if it is overcast," Halaris said. "Expose your eyes to natural light for one hour each day. At home, open the drapes and blinds to let in natural light. SAD can be effectively treated with light therapy, antidepressant medication and/or psychotherapy."

If you feel the blues because you're lost in grief, Loyola bereavement counselor Nancy Kiel suggests that it's important to acknowledge your loss.

"Start a new tradition to honor and remember your loved one," Kiel said. "Light a special candle or at dinner, have everyone share a favorite memory or all can take part in a loved ones favorite holiday activity. Do something that would make your loved one smile."

She also suggests that you avoid shopping at the mall -- go online instead -- and focus on being around people who are caring and supportive.

More information

Learn more about depression at the U.S. National Library of Medicine.