The start of December means two things: The holiday season is officially upon us, and winter is coming. The days are getting noticeably shorter, as the nights grow longer, in anticipation of the arrival of the winter solstice, December 21, also known as the shortest day of the year and the beginning of winter. Unsurprisingly, the cold weather means we're more likely to get sick (i.e, the common cold, the flu), but the cold could affect us in unexpected ways — both physically and mentally.

Weather can have a profound impact on our health and well-being. Freezing temperatures can influence our thoughts and decisions without us realizing it. Science has found it can affect everything from creativity to our susceptibility of developing migraines.

Read More: Why Does The Weather Influence Our Chances Of Catching A Cold?

Below are six surprising ways how cold weather can affect us physiologically and psychologically, for better or for worse.

Physical Effects

Migraines

The research is not concrete, but anecdotally speaking, there's an exceptionally high number of migraines cases during the winter months. Extremes in weather, like big swings in temperature and barometric pressure, can influence the likelihood of a migraine, according to the Cleveland Clinic. This effect occurs more in people who are prone to migraine and tension-type headaches.

In a 2015 study published in the Journal of Headache and Pain, researchers asked 66 patients to provide headache diaries from several months in 2007 to a headache clinic in Taiwan. A total of 34 patients reported sensitivity to temperature change while the other 32 did not. Researchers compared the headache diaries, and found patients who were sensitive to temperature experienced a significantly higher number of headaches in the winter than in the other seasons.

Although the association between temperature and headache is not fully understood, one researcher hypothesized these headaches may be linked to blood vessel and circulatory changes, which cold weather might aggravate.

Heart Complications

The cold weather can lead to a vast increase in heart complications. The cold air makes the body work overtime, especially the lungs and the heart. Cold temperature is known to raise blood pressure, and also increase levels of certain proteins that could increase the risk for blood clots.

A 2010 study published in BMJ found cold weather may increase the risk of a heart attack. Every 1.8 degree Fahrenheit reduction in temperature on a single day was associated with about 200 additional heart attacks. When the weather is cold, the heart must also work harder to maintain body heat, and the arteries tighten, which restricts blood flow and the oxygen supply to the heart. All these factors could trigger a heart attack, especially in the elderly, or those with existing heart disease.

Low Sex Drive

Winter time means we're less likely to have a higher sex drive. The body’s testosterone products naturally declines from November through April in the Northern Hemisphere, and then rises steadily through the spring and summer with a peak in October. This is why reproductive rates increase, with the month of June showing the highest rate of conception.

Read More: Low Sex Drive In Women Before Last Period Depends On Race And Ethnicity

A study conducted by the University of Tasmania suggests our ancestors' hibernation patterns are to blame for the drop in libido. "Hibernation caused their metabolisms to slow and sex drives to wane, as they increased their calorie load and slept more," said Dr. Margaret Austen, co-author of the study.

Mental Effects

Depression, But Less Violent

The link between winter and depression is seen in patients who suffer from seasonal affective disorder (SAD). This could be attributed to several reasons, such as the decrease in sunlight may disrupt the body’s internal clock, leading to feelings of depression; reduced sunlight can lead to a drop in serotonin levels, and trigger depression; or the change in season can disrupt the balance of the body's level of melatonin, which plays a role in sleep patterns and mood, according to the Mayo Clinic.

Meanwhile, violent thoughts tend to decrease during the winter time, while levels of violence and aggression are higher in hot climates, according to a recent study in Behavioral and Brain Sciences.

Boost Creativity

Various types of creativity can occur, depending whether we feel hot or cold. In a 2014 study published in Acta Psychologica, researchers found people who were given a heated therapeutic pad, a hot cup of tea, or who were in a warm room, were better at creative drawing, categorizing objects, and thinking of gift ideas for others. Meanwhile, those in the cold were better at identifying metaphors, thinking of new pasta names, and planning abstract gift ideas. The researchers hypothesize warmth helps people feel psychologically connected and more generous to others, while the cold may stimulate referential, or cold precessing, as people are more likely to feel distant from others.

Read More: Creativity Doesn't Always Stem From Thinking Outside The Box

Wear Red

Winter can affect what we wear, specifically what color we choose, but during a certain time of the month. A 2014 study in PLOS ONE found women are more prone to wearing red or pink on days when they’re ovulating, specifically in the winter. Although the link remains unclear, researchers hypothesize red and pink exude sex appeal in the winter, a time where women are limited to the ways they can dress seductively. The red-dress effect can be moderated by current climate changes, and does provide further evidence that under certain circumstances, red and pink is reliably linked to female fertility.