Not all of us find ourselves tapping our toes along with “Jingle Bells” during the holidays. For some, days meant to be jolly are about as much fun as sour eggnog.

The "holiday blues" is sadness, anxiety, and sometimes depression that manifests during the holiday season. For some people, it inevitably comes along with each winter's gloom. 

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For example, someone who lost a best friend on Christmas Eve 20 years ago may not feel like going caroling this year either.

“That's when we have these particular illnesses, deaths, or trauma,” said Sam Moreno, a psychologist at the Robert Young Center for Community Mental Health in Moline, Ill. “The holidays trigger some kind of past unpleasantness, and it permeates them.”

Others prefer not to be reminded of their family's dysfunction and loathe annual get-togethers.

“Many people have had unpleasant situations throughout the holidays via a function of families and personalities,” Moreno told Healthline. “They look at the holidays, and they're not what we see on TV or the movies.”

Plus, burning the candle at both ends takes a toll. Leading up to the holidays, we work extra hard to prepare for time off, while at the same time cooking, shopping, and planning parties. “Afterward, some people are just down,” Moreno said. “You need to rest, sleep, and take care of yourself.”

On the flip side, going back to everyday life after the holidays sometimes seems bland and depressing. “I usually say to people who tell me they like the holidays, 'That's great. But what are you going to do in January? And February?'” Moreno said.

Lastly, if you feel despondent regularly during the dark winter months you may have seasonal affective disorder, or SAD. While little is known about SAD, researchers at Yale University hope to find some answers soon. Experts theorize that this type of seasonal depression may be triggered by a lack of UV light from the sun, and some recommend spending time beneath a UV lamp.

People with SAD often crave sugar, overeat, and generally become lethargic and withdrawn. Symptoms may begin as early as September and last until April. More than 11 million Americans suffer from SAD, and research shows women may be four times as likely to have SAD symptoms as men. 

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It's very important to maintain realistic expectations, Moreno said. “We can be mostly responsible for our own efforts, but we can't predict the outcomes. A person has to remember, 'I've got to be happy with myself for cooking this because I'm doing my best, but I realize some people might not like it or come to my party.'” 

Besides UV light therapy, another approach to treating SAD involves teaching someone how to change the way he or she thinks about and reacts to wintertime sadness. This is known as cognitive-behavioral therapy, and clinical trials are currently under way at the University of Vermont to measure how well it works for people with SAD.

If symptoms persist for more than a couple of weeks or sadness begins to affect your work or home life, it's a good idea to be evaluated for depression by a mental health professional.