Back in the day your 20s might have been a serious decade where you settled down, had some kids, bought a house, etc. But now, for those blessed to be free of family constraints or serious debts, a rising marriage age and longer career onramps can make the third decade of life seem -- from the outside at least -- like one big party.

Without kids or a mortgage and with the whole world to explore, what do young people have to do but socialize, experiment, and enjoy, this thinking goes. And those of us who are just a little bit older but more tied down often even remember the decade this way -- as a halcyon period of late nights (not due to dirty diapers or work deadlines), carefree weekends, and untethered ambition.

But does the data back up this vision of your 20s as a generally enjoyable decade?

The quarter-life crisis is actually a real thing.

Not at all, says Ran Zilca, Chief Data Science Officer at happiness app Happify, in a fascinating recent HBR post. According to his company's data, your late 20s is actually generally a bummer. The quarter-life crisis, he contends, is a real thing.

It's easy to joke about a so-called "quarter-life crisis" caused by an unfulfilling entry-level job or a run of bad dates, but when Happify looked at information on 88,000 users, it discovered that these early life issues aren't funny at all for those living through them. "We found evidence both for the prominence of the quarter-life crisis and for the rise in well-being that follows it. Looking first at self-reports of ongoing stress, we found that people experience a sharp increase in stress levels in their late twenties and early thirties," he says.

Zilca also notes that other research points in the same direction, with several recent studies showing that "being in your twenties is often confusing and lonely." Interestingly, the average age for the onset of depression has also dropped from middle age to the mid-twenties, he notes.

What's making our late 20s so miserable?

A couple of factors are behind all this gloomy data, Zilca claims. He notes that our late twenties is the first time many of us are truly cut free from the educational ties and family environments that previously cocooned us. But while many 20-somethings suddenly lack much of the support they've long been accustomed to, at the same time they're not given the respect of fully fledged adults.

"As they attempt to establish their status as adults, their environment sends them mixed messages: regardless of their professional or personal achievements, they are still considered by others to be 'kids,' especially before they marry and have children," writes Zilca.

In the full post Zilca goes on to describe the four stages of the typical quarter-life crisis, as well as how people tend to recover from one (hint: it's more about coping strategies than any objective decrease in stressors). Check it out if you're in the midst of the late-20s blues yourself, or if you know someone who could use all the wisdom they could get on the period and its challenges.

For the rest of us who are now solidly past our 20s, the post might be a healthful reminder not to lose perspective and forget the era's struggles in favor of its charms. Plus, next time you talk to a younger person about their "quarter-life crisis," you might be inclined to take them a little bit more seriously.

How did you find your late 20s -- mostly fun or a whole lot of stress?