As you may know, it was the eminent psychiatrist Lucy Van Pelt who first discovered, diagnosed, and named the condition.
In one of her early disquisitions on the topic, Van Pelt described post-Christmas letdown this way:
I know how you feel about all this Christmas business, getting depressed and all that. It happens to me every year. I never get what I really want. I always get a lot of stupid toys or a bicycle or clothes or something like that.In her own case, of course, she linked her disappointment and depression for not receiving the gift of real estate.
Not getting what one hoped to or expected to receive can naturally lead to disappointment (see the work of R. Parker, "Red Ryder Dismay: The Physiological Effects of Denial, and the Ophthalmological Effects of Acquisition").
Thing is, I get rather sad after Christmas even now, and I'm not bothered by what I got or didn't get as a gift. I have not lost any dear ones in some time, deaths that leave an acutely painful space at the dinner table. I'm not one who is saddened by the holidays, although I can let myself get stressed. All I can think of that causes my blue state is what we casually refer to as an emotional hangover, a feeling of sadness or even desolation that comes at the end of any event that excites high emotion. I knew a woman who was so sad after her wedding that her beautiful island honeymoon was almost ruined.
So is this a real thing, this post-Christmas (or other emotional event) letdown?
Researchers at NYU and other universities have found that strong emotion does affect memory in significant ways, notably improving memory of non-emotional events that follow emotional events. This new study doesn't say that emotional events leave one feeling sad, but there is clearly a physiological effect on the brain.
On one hand it seems silly to have to come up with a label for the sorrow we feel when something we enjoy and have looked forward to is over. On the other, post-Christmas letdown (or PCL) seems quite common, and fairly strong. As usual, I think Charles Schulz was onto something.
Since the boffins like to label everything, I think they could do worse than an official title of Post-Christmas Letdown. If that's too calendar-specific for people like my friend with the post-wedding blues, maybe Post-Event Affective Disorder, or PEAD. Not as catchy as SAD, though. In any event, it is usually over by Epiphany, so there's probably no need to prescribe anything for it. Take two gingerbread men and call me in the morning.