Do your adult kids treat your home like a hotel? You could be suffering from 'Intercontinental Syndrome'.

Lucy’s oldest child Zoe will be turning 18 and starting uni next year. Lucy is expecting a few things to change around the house.

“When you’re the parent of an HSC student, you’re very indulgent that year, because the whole world tells you how hard it is for them,” Lucy says. “You completely lay off them for a year. They don’t have to be responsible for anything.”

Next year, Zoe will still be living at home. But Lucy is expecting her to be more “adult”, and to start contributing to the household.

“I definitely won’t be doing things for her that I was doing and I definitely expect her to have a regular job and to pay for her own stuff,” Lucy says.

“I’d like one meal a week and a load of washing a week and a tidy bedroom. I’ve done this for 18 years now and I’m tired.”

Meanwhile, Diane’s daughter Bree is 21. She’s at uni, working part-time and living at home so she can save up enough money for a house deposit. She pays $50 a week board and she’s meant to help out around the house.

“I tried the ‘Okay, you’re an adult now, you’ve got adult responsibilities’ line and it just didn’t work,” Diane says. “I said, ‘Right, you have to be responsible for keeping the bathroom clean,’ and it just didn’t get done.

“I got so embarrassed when we had guests and they took a shower and then I realised the shower had mould in it and the bathroom sink was full of hair and toothpaste. I was getting so uptight that it wasn’t being done. Now I just do it.”

Diane says Bree complains that she treats her like a child.

“I don’t know if I treat her like a child because she behaves like one, or she behaves like one because I treat her like one.”

All around Australia, parents are facing the same issues. Due to rising house prices, more time spent in higher education and a later average age for marrying, kids are taking longer and longer to move out of home. In fact, almost one in 10 people in their early thirties is still living with their parents.  Social researcher Mark McCrindle says there’s no longer any social stigma around it.

“There’s no real push factor to get them to move out,” he tells Mamamia. “It is a new reality, this multi-generational household.”

So what happens when your children become adults but don’t move out? How do things change? What are the new rules to live by?

Psychologist Dr Michael Carr-Gregg says a lot of young men and women basically treat the family home as a hotel.

“I call it the Intercontinental syndrome,” he adds.

He says there are three reasons why parents let their kids get away with it: because they’ve never been authoritative, because they want to avoid conflict, and because they feel guilty about not having spent enough time with their kids.

“They feel that maybe they owe their children something. I find it really quite bizarre, because many of these kids get a very good ride.”

Dr Carr-Gregg believes that from the moment they finish high school, kids should be contributing to the household. He says when his own son lived at home in his early twenties, he would cook at least once a week, as well as doing cleaning, laundry and shopping.

“It seems to me that it’s perfectly reasonable to expect essentially adult children to not only pay their way but contribute,” he adds.

Meanwhile, psychologist Muriel Cooper believes grown-up children still living at home should obey the rules of a normal share house. That includes cleaning up after themselves and doing their own laundry.

“Do yourself and your kids a favour, and teach them how to look after themselves,” she says, “because if you do everything for them, you are setting them up for a lifetime of dependence and disappointment.”

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Cooper believes kids should get used to contributing financially, beginning with their first part-time job, even if it’s a paper round in their teens.

“If you’re wealthy, you think, ‘Oh, I don’t need their money,’” she adds. “But the money is symbolic.”

As for the question of adult kids having their boyfriends or girlfriends sleeping over, Dr Carr-Gregg says parents need to make a decision about what’s acceptable, and then let their children know.

“There are some parents that don’t mind and in fact quite welcome it,” he says, “because they prefer their children to have such experiences in the relative safety of their own home, as opposed to in the disabled toilets at David Jones – and that does happen.

“I personally would encourage parents to allow it, and also, if they’ve got boys, I’d put a large amount of condoms in the top drawer and say, ‘No one’s counting.’”

Having adult children living at home does have its drawbacks for parents, especially if the kids aren’t paying their own way. But McCrindle says when baby boomers complain, it’s done with a bit of warmth.

“I think, actually, the boomers do appreciate having their young people around a little bit because it does keep them in touch with the next generation a bit more. It does mean that the baby boomers don’t have to think about the next life stage of being empty nesters and the fact that the family years have been concluded.”

Cooper says she sometimes has parents consulting her because they’re struggling with the idea of becoming empty nesters.

“The thought of them not having their children around is very problematic. Some parents will do anything to keep their kids at home.”

As for Diane, she enjoys having Bree living with her.

“We spend some time together. She bought all the box sets of Made In Chelsea, so we both sit down and watch it. I do still like having her around.”