Though some people dread having to see their family around the winter holidays and don't enjoy Christmas shopping and the colder weather, others feel more depressed after the holidays are over, since they have to go back to the same routine, among other haunting realities. This is known as post-holiday depression. This can start after Christmas or similar holidays and/or after New Year's Day, depending on when a person celebrates.
According to an article on www.psychcentral.com, the possible causes of post-holiday depression are "unmet expectations, unrealistic resolutions, and a return of loneliness and guilt about overindulgence." For example, perhaps someone trys to give all her friends and family members gifts
and fails. Maybe a different person overspends and purchases gifts for everyone and is now in debt. Another person might try to lose 10 pounds after Christmas but just can't get motivated. Yet another might return to another state, away from family members. These all can happen and don't feel very uplifting, which can lead to depression in some people.
The author of the article suggested that people treat the holidays no differently than any other time of the year. Just because it's Christmas, Hanukkah or another holiday, it doesn't mean everyone has to pretend to be happy when they're not. That can be depressing by itself.
Post-holiday depression generally only lasts for a short period of time. If the depression lasts longer, it can be classified as a more "serious" type of depression, though all types of depression should be regarded with care. According to an article on Suite 101, post-holiday depression is considered more of a mental distress than a mental disorder, since it's so fleeting and makes a minimal impact for the most part on the person who has it.
The idea that post-holiday depression is short-lived can be found in an article from www.PennLive.com. The article compares seasonal affective disorder to post-holiday depression, saying that "SAD isn’t the post-holiday blues people tend to get in January or the cabin fever resulting
from being indoors for too long on shorter days and in inclement weather."
Symptoms of post-holiday depression are the same as during the holidays or during any type of depression, though of course they are less severe and probably for different reasons. According to the University of Maryland's Medical Center Web site, some symptoms of the "holiday blues" are
headaches, difficulty sleeping or oversleeping, weight and appetite differences, and agitation and anxiety, among others.
On a fact sheet found on Mental Health America's Web site, people with post-holiday depression are given some recognition, though there is more of a focus on depression during the holidays and for seasonal affective disorder. The suggested cause for post-holiday depression is
"disappointments during the preceding months compounded by the excess fatigue and stress."
There is mention of people having more illnesses after the holidays in a Psychology Today blog, which can be linked to stress and the "let down effect." This effect is characterized as "a condition where high energy or activation levels in the body are immediately followed by a rapid drop in activation levels." The stress and more joyful feelings during the holidays (at least for some people) can leave a person depleted physically after the highstrung feelings of the holidays are over. Perhaps the mind and body can both be sick, in a sense, after the holidays.
Sources:
http://psychcentral.com/lib/2006/wrung-out-by-ringing-in-the-holidays-dealing-with-post-holiday-blues/
http://depressiongrief.suite101.com/article.cfm/understanding_postholiday_depression
http://www.nmha.org/index.cfm?objectid=c7df954d-1372-4d20-c80ed0a7ab69d250
http://www.psychologytoday.com/blog/5-cents-the-doctor-is-in/200912/when-the-good-times-make-us-sick-avoiding-post-holiday-illness-
http://www.pennlive.com/bodyandmind/index.ssf/2009/12/it_might_be_more_than_just_the.html
http://www.umm.edu/mentalhealth/holsymps.htm