Variety of Christmas cookies and sweets. Top view over a dark stone background. Holiday baking concept.

(© Jenifoto -

LAWRENCE, Kan. — The holidays are supposed to be “the most wonderful time of the year,” but for many it can actually lead to higher levels of depression than usual. If you’ve been feeling especially blue this year, a new study suggests getting those visions of sugar plums out of your head right away. Researchers at the University of Kansas say that the added sugars found in virtually all holiday sweets can induce metabolic, inflammatory, and neurobiological processes that are connected to depression and negative feelings.

These sugary treats, combined with dwindling amounts of sunlight in the wintertime and subsequent sleep pattern variations, can create a “perfect storm” of depression during the holidays.

“For many people, reduced sunlight exposure during the winter will throw off circadian rhythms, disrupting healthy sleep and pushing five to 10% of the population into a full-blown episode of clinical depression,” comments Stephen Ilardi, KU associate professor of clinical psychology, in a university release.

It’s also a possibility, according to the research team, that seasonal-depression symptoms will push individuals to start eating more sweets. This will, in turn, only create a vicious cycle of feeling down and eating treats to feel better, only to end up feeling even worse.

“One common characteristic of winter-onset depression is craving sugar,” Ilardi continues. “So, we’ve got up to 30% of the population suffering from at least some symptoms of winter-onset depression, causing them to crave carbs – and now they’re constantly confronted with holiday sweets.”

It can be especially hard for people feeling down to resist sweets because they do offer an initial mood boost. But that effect is similar to other substances considered much more harmful, like alcohol. And so, the short-term mood benefits of sugar consumption are largely outweighed by the havoc large amounts can wreak on the body.

“When we consume sweets, they act like a drug,” Ilardi says. “They have an immediate mood-elevating effect, but in high doses they can also have a paradoxical, pernicious longer-term consequence of making mood worse, reducing well-being, elevating inflammation and causing weight gain.”

The research team came to their findings after analyzing a large assortment of previous research focused on the physiological and psychological effects of eating added sugar. All in all, researchers say the inflammation caused by excess sugar is the number one contributor to depressive thoughts.

“A large subset of people with depression have high levels of systemic inflammation,” he says. “When we think about inflammatory disease we think about things like diabetes and rheumatoid arthritis – diseases with a high level of systemic inflammation. We don’t normally think about depression being in that category, but it turns out that it really is – not for everyone who’s depressed, but for about half. We also know that inflammatory hormones can directly push the brain into a state of severe depression. So, an inflamed brain is typically a depressed brain. And added sugars have a pro-inflammatory effect on the body and brain.”

Interestingly, the way in which sugar impacts the bacteria present in our bodies is likely another big factor in its depression-inducing capabilities.

“Our bodies host over 10 trillion microbes and many of them know how to hack into the brain,” Ilardi explains. “The symbiotic microbial species, the beneficial microbes, basically hack the brain to enhance our well-being. They want us to thrive so they can thrive. But there are also some opportunistic species that can be thought of as more purely parasitic – they don’t have our best interest in mind at all. Many of those parasitic microbes thrive on added sugars, and they can produce chemicals that push the brain in a state of anxiety and stress and depression. They’re also highly inflammatory.”

Ilardi recommends a diet of non-processed foods, particularly rich in plant-based foods and Omega-3 fatty acids, in order to combat depression on a dietary level. Furthermore, the study’s authors recommend staying away from added sugars year-long, not just during the holidays.

The study is published in the scientific journal Medical Hypotheses.

About John Anderer

Born blue in the face, John has been writing professionally for over a decade and covering the latest scientific research for StudyFinds since 2019. His work has been featured by Business Insider, Eat This Not That!, MSN, Ladders, and Yahoo!

Studies and abstracts can be confusing and awkwardly worded. He prides himself on making such content easy to read, understand, and apply to one’s everyday life.

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