Many people experience seasonal depression during cold winter months as they long for more sunlight, and some are diagnosed with seasonal affective disorder, which causes symptoms like loss of energy, difficulty concentrating and eating more, according to the Mayo Clinic.

But these widely talked about ways that winter affects mental health are not the only ways the season influences mood and behavior, according to a recent study published to Sage Journals.

In the study, researchers observed population-wide changes in eating behavior, sexual activity and ability to focus.

The authors of the study added that “seasonal variation in mood is common among the general population,” citing a study analyzing 509 million tweets from over two million people worldwide. Decreased sunshine was associated with more negative tweets.

Since animals are largely impacted by different seasons, the study asserts the importance of knowing how the seasons impact humans, as well.

Winter dryness may contribute to increased eating

The study claimed that people’s diets are typically at their worst during the winter.

The season holds some of America’s most gluttonous holidays, including Thanksgiving and Christmas. Average holiday weight gain among adults is roughly one pound. However, this number is usually higher among people who are already overweight or obese, according to a study in the National Library of Medicine.

Aside from the holidays, an increased appetite may come from temperature drops and humidity levels. A study from 2018 found that drier weather increased the feeling of hunger. Since lower temperatures typically bring lower humidity levels, people may eat more during the winter.

The study suggested another factor adding to the change in eating behavior is clothing choice. During the summer, people feel more motivated to look their best because they can’t hide beneath layers.

Sex rates peak around Christmas and early summer

U.S. birth rate data over the past 78 years suggests conception has biannual peaks in autumn and winter, the recent study said.

Abortion rates and sexually transmitted disease diagnoses similarly “peak in the months following Christmas and in late summer,” researchers noted.

Winter alters focus

A study published by PNAS in 2016 explained that sustained attention is at its best around the winter and summer solstices.

Researchers gave 28 young adults in Belgium (14 men and 14 women) a “sustained attention task” and a “high-order executive function task” at various points in the year, to test whether seasonality influences focus.

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Results “varied significantly across seasons,” but the scientists observed annual patterns suggesting that sustained focus peaks in the winter and is at its worst in the summer.

Meanwhile, the severity of dementia and Alzheimer’s disease symptoms seem to be worse in the winter and spring, according to a study published by Plos Medicine. The study said seasons are “a clinically significant association with cognition.”

Seasonal affective disorder symptoms include “difficulty concentrating, remembering or making decision,” according to the National Institute of Mental Health. The study didn’t say whether this worsened ability to focus is a byproduct of other symptoms like worsened diet, restlessness and anxiety or is due to something else.

However, food has a direct influence on brain health, and some foods are much better for cognition and mental health than others, as the Deseret News previously reported.

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