For some people, winter doesn't just bring cold and snow - it also brings a host of health problems, including depression and heart attack.
Here are seven health woes that are more likely to rear their heads in the colder months than during other times of the year.
Although holidays such as Christmas and Hanukkah seem to lend themselves to heartwarming happiness, many people develop depression and anxiety during the holiday season, said Dr. Ronald Podell, medical director of the Center for Bio-Behavioral Science in Los Angeles and author of "Contagious Emotions: Staying Well When Your Loved One Is Depressed" (Atria, 1992).
People get sad around the holidays because there is "a cultural image that all of us understand, and you experience a significant discrepancy between yourself and that image" of happiness, Podell told MyHealthNewsDaily.
Two groups of people are most vulnerable to the holiday blues: Those who don't have close friends or family and feel lonely and abandoned during the holidays, and those who feel anxiety and stress stemming from visits with dysfunctional relatives, Podell said.
Cold weather ramps up the risk for heart attack, according to a study published in August in the British Medical Journal.
Researchers from the United Kingdom found that for every 1-degree Celsius (1.8-degree Fahrenheit) drop in the average daily temperature, there is a 2 percent increase in heart attack risk.
That translates to 200 additional heart attacks for each 1.8 degree Fahrenheit (1 degree Celsius) reduction in temperature on any given day, the study said.
Winter can worsen high blood pressure, and therefore trigger complications such as heart failure and stroke, according to a study published in January in the journal Frontiers in Bioscience.
"Extremes in temperature changes - from warm to cold - can increase your blood pressure and cause your blood vessels to constrict," said Dr. Joseph Hanna, chief of neurology at the MetroHealth health care system in Cleveland.
Aneurysms - which are blood vessels that bulge due to a weakening in their walls - in the brain are more prone to rupture, prompting a stroke, when the shape of the blood vessels changes, Hanna told MyHealthNewsDaily.
Seasonal affective disorder
Seasonal affective disorder is a type of depression. People with this disorder have dampened moods in the winter months, when the effects of short days take their toll (January and February), according to the American Psychological Association (APA).
Evolutionarily, humans are inclined to sleep and be lazy in the winter. Researchers think the disorder stems from failure to adapt to the physical environment, the APA said.
To cope, health experts recommend using light therapy - exposing yourself to extremely bright light a few times a day - to alleviate the symptoms of SAD, according to a 2006 article in the journal American Family Physician.
In the northern hemisphere, people always seem to get sick during the winter months, from November to March. One reason is the influenza virus's ability to survive: A 2007 study on guinea pigs in the journal PLoS Pathogens found that influenza is more stable in cold, dry air.
Researchers from Mount Sinai School of Medicine in New York City found that low humidity, around 20 to 30 percent, provided the optimal chances for influenza's survival, whereas survival was impossible at humidity of 100 percent.
And guinea pigs transmitted influenza virus to each other at 5 degrees Celsius (41 degrees Fahrenheit) more than at 20 degrees Celsius (68 degrees Fahrenheit). No transmission of the flu was seen at 30 degrees Celsius (86 degrees Fahrenheit), the study said.
Chlesterol levels are highest in the winter and lowest in the summer, according to a 2004 study in the journal Archives of Internal Medicine.
Out of 517 healthy people, 22 percent more people had high cholesterol (240 milligrams per deciliter of blood, or higher) in the winter months than in the summer months, according to the study.
The change in cholesterol levels could be attributed to people exercising less in the cold months, the study said, though more research is needed to find the exact reason why.
As many as 7.5 million people in the United States have psoriasis, a disease that causes red lesions and scaly skin, according to the National Psoriasis Foundation. The disease is aggravated in the winter months, when dry air, decreased sunlight and colder temperatures can prompt flare-ups.
Thirty percent of wintertime dermatologist office visits are for psoriasis, compared with 20 percent of summertime dermatologist visits, according to a 2004 study in the International Journal of Dermatology.
Pass it on: The winter months can be the cruelest months if you have diseases or conditions such as psoriasis, high cholesterol or seasonal affective disorder.