Try and spare a thought for psychologist Carole Slotterback. She spent years studying everything she could find on the history and culture of Christmas, only to write a book that struggled to find a publisher willing to take a chance on it. Good thing The Psychology of Santa has become a hit, then.

"Oh, I never expected the attention,” she admits from her office at the University of Scranton in Pennsylvania, where she has recently been interviewed by CNN and the Associated Press, "but I’m having fun."

The fun started several years ago when she began studying letters to Santa with her students. Intrigued, she eventually asked the postmaster for more. Those letters - thousands and thousands of them from Scranton children - kick-started the research by painting an initially predictable picture of American youth: kids want stuff, and aren’t shy in asking for it. But many of the children asked for more than just the hot toy of the moment.

"They ask for presents, but they do want time with their parents and their families,” Slotterback says. “With some of the children, that was all they wanted, to be with their families or to not have their parents be fighting for once."

The letters were certainly varied in their scope. "Someone asked for ham, so that he could have ham and eggs Christmas morning, some children sent copies of their homework to prove they were being good, some asked for world peace." Some were also harrowing.

"One of the saddest ones we had was a year there had been a fire here in town and a little girl had been killed. One of her friends wrote in and said she didn’t want any presents, she just wanted her friend to be alive again so she could play with her. She said she knew it would be a stretch, but that is what she wanted most for Christmas. Santa is more complex than the adults tend to think. A child views Santa as an authority figure and being kind of God-like, in some ways."

Slotterback has a child of her own, an 8-year old boy who at the time of our conversation was drafting his own letter to post to the North Pole. Has her own child questioned Santa’s existence? After all, he enjoys a unique opportunity of asking perhaps the world’s now-leading expert on the topic.

"He asks questions from time-to-time,” she says. “But don’t be afraid to answer what children ask and to answer them honestly. Kids are going to hear what they want to hear. Even if you go into a half-hour explanation, they’re going to pick out a thirty-second soundbite that suits them, and that’s what they’ll focus on. So just answer their questions. Most kids find out the truth gradually, I think. There’s just so much at stake in believing in it."

The Santa myth is powerful, but Slotterback believes that any negative effects in spreading it are negligible, and are offset by the joy that believing in St. Nick brings. She interviewed several hundred college students about their Christmas experiences and had only one person speak negatively about discovering the truth - and that was because, amazingly, her father told her Santa had died of a heart attack and wasn’t coming that year. But that doesn’t mean that Christmas cannot be a difficult time for those of us who stopped believing in Santa.

"There’s so much emphasis on family, and if you don’t have a family, it can be difficult. If you’ve had a loved one die, getting through that first Christmas is a devastating thing. So there is some depression there, but not to the extent that some people try to suggest. If you look at psychiatric emergency room admissions, for example, you see a decline in the weeks before Christmas, and then one to three weeks afterwards you’ll see an increase, but of the same magnitude as the decline before. So you see a little dip before the holidays that goes back to normal afterwards."

Santa then, could be our attempt to protect children from grimmer futures that may await them. But that would not explain why the myth is still so remarkably pervasive.

"I’m not certain why. For some, it reminds them of their happy times in childhood. Certainly our advertising culture picks up on Santa and glorifies it - you can’t get away from it. Even Jewish children believe in Santa Claus. Due to ads, Jewish parents now try and make Hanukkah bigger so their children feel better."

So is Santa Claus still a good idea?

"I don’t think it’s bad, certainly. But I don’t like the advertising and I don’t like the pressure put on people to buy things. This is just me personally, but I like my holidays in order - Halloween, Thanksgiving, then Christmas. But now you start getting Christmas imagery in August and it disturbs me," she says, chuckling a little over her frustration.

Which brings me neatly to what I had wanted to ask all along: are you sick of Christmas at all yet? Even just a little bit?

"No, no,” she laughs. "What keeps me going is my son’s reaction to it and his own excitement for it all. I just really enjoy that." As her book says, we give because of what it gives back to us.