Elvis knew all about it when he sang: "It will be lonely this Christmas without you to hold." While the festive season brings fun, parties and feasting, for single people it can often mean a spell of doubt and self-questioning about their lives. Every Christmas, card and song revolve around the central theme of happy families. Invitations to Christmas parties will sometimes have the dreaded "and partner" addition. Even if single people get through the build-up to Christmas without feeling isolated, Christmas week itself can be unnerving.

"The gap in people's lives becomes apparent at Christmas," says Michael O'Donnell, a consultant at Circles Club, a dating agency. "They are more concerned at this time of year about family, close friendship and companionship."

While families and couples hide themselves away during Christmas week, single people can feel left out.

"During that week, single people will think: `I don't want to spend another Christmas on my own,'" says O'Donnell. As a result, people flock to the dating agencies in January. "The phones start hopping after St Stephen's Day. It would be one of the busiest times of the year," he says. Often people will make New Year's resolutions that they will become more active in searching for a partner and, when traditional methods fail, the dating agency becomes an option.

Rachel McGrath, director of the dating agency Who's Who For The Unattached, says that while December is often the slowest time of the year for her service, January is the busiest. The agency sees a 40 per cent increase in clients during the post-Christmas period, she says.

"The New Year's resolution is a big thing," says Jacqueline Dowling of Elite Introductions, another dating agency. "Everybody looks at their lives around the New Year and Christmas. It can be a sad time of the year for some people."

Those coming into the dating agency talk about the loneliness of Christmas Day and New Year's Eve, but the lead-up to Christmas can also be hard. "People have to go to parties and they don't want to appear at the office party alone. They might not usually be asked to bring someone to parties, but they would prefer to be seen with a partner," Dowling says.

Although the party scene might seem like an opportunity to meet people, nightlife doesn't always offer the answers for single people. "There is very little in Dublin to cater for single people. It's a buzzing young city, but that doesn't mean it is easy to meet people," Dowling says.

Dowling says all types of people can find themselves lonely at Christmas: people coming back from living abroad who suddenly find their friends married with children; older and younger people who find the singles scene too challenging; and those who have recently split up.

Apart from being a lonely time for some people, Christmas is also notorious as a catalyst for the break-up of relationships. "An awful lot of infidelities happen around Christmas, and the pressure of Christmas also makes some people split up." says Georgina Zafar, information officer at Gingerbread, a support group for people parenting alone.

"I've had calls from people saying `I discovered my husband is having an affair', and things come to a head over the holidays," says Zafar, whose job is to talk to people who ring or call in with problems. A combination of being together in the house for a long period of time and financial pressures can force bigger issues to the fore over the festive season.

New Year's resolutions can have the effect of spurring people on to get out of a relationship. "Some people might think: `It's a New Year and I'm not spending another year in that house,'" Zafar says.

For single people with children, Christmas can be a difficult time as financial pressures build up and the reality of parenting alone comes into focus. "Some people are dreading Christmas on their own if they have a child. Then other people are so busy preparing for Christmas, but afterwards the pressures hit them," Zafar says.

Whatever the circumstances, Christmas this year will no doubt be a difficult time for some people, with or without significant others. But the New Year can offer a fresh start and new opportunities.