"We grew up in a world where we could take it for granted that the self came first," she said. "The downside is that a lot of people spend their 20s doing things they think will make them happy, but end up lonely and depressed."
Part of the problem, she believes, is the chasm between where her generation finds itself today and the lifestyle their parents had achieved by 30.
"Most parents bought their house in 1968 for $65,000, but it would go for $800,000 today, so they don't really get how hard it is to get by," Ms. Twenge said. "At the same time, they are very rightly pointing out, 'Look, you're not putting down roots, you're not making any commitments, what are you going to do when you hit 30 and you haven't held a job for longer than a year?' "
But the priorities of today's thirtysomethings have little to do with those of their parents.
A Pew Research Center poll released in January showed that 81 per cent of 25-year-olds in the United States said getting rich is their generation's most important life goal. Fifty-one per cent said the same thing about getting famous.
While researching her play, Ms. Duncan was told by several straight-faced subjects that they had expected to be a movie star or millionaire by age 30. Others seemed genuinely upset they had not become legends by their late 20s.
"I always thought I would die at 27," one woman named Kendra said. "I never pictured myself older than 27, so on my 28th birthday, I was like, 'Wow, here I am. I didn't really make plans for this.' "
Mike Gayle, the British author of the angst-filled novel Turning Thirty, admits on his website that he actually expected to marry Madonna by the time he hit the big 3-0.
"I've lost count of the number of times I've read interviews where some twentysomething celebrity begins a sentence with the words: 'By the time I'm 30 ...' then reels off a long list of things they hope to achieve," he wrote on his blog. "I think we've all done that at some point."
Ms. Twenge said the tendency to dream big is not new, but lasts longer with today's young adults. "Kids in the 1930s dreamed of being baseball players, but reality intruded a lot sooner," she said. "Now we grow up thinking we're going to be rich and famous, and when we hit 30 and that hasn't happened yet, we wonder what's going on."
That reality can send many people into what has been dubbed a "quarter-life crisis," something New York journalist Doree Lewak is trying to avoid while researching her book, The Panic Years: A Survival Guide to Getting Through Them and Getting on Your Married Way, to be released next year.
"Thirty is the first birthday in our lives when we really start to take stock of where we are and where we should be," the 27-year-old said recently.
For her, the panic is related to the personal aspects of her life, not the professional.
A successful journalist and published author, Ms. Lewak said that she had concentrated so fiercely on success in her work that she delayed settling down and having kids, the ultimate measure of success in her parents' eyes.
On her past birthday, she received a gift certificate for a dating service.
"All these subtle hints from your loved ones really help," she said. "There's a tremendous pressure from family, I call it panic by proxy."
But while Ms. Lewak believes there are ways to remain calm in the face of 30, she says the anxiety is really just a part of being raised with sky-high expectations.
"It just comes down to wanting it all."
