It hasn't been a great month for American optimists. First came the much reported research from recent Nobel laureate Angus Deaton and his wife Anne Case showing that the mortality rate of middle aged whites is rising due to suicide and substance abuse. Now, new findings from psychologist and author Jean Twenge are adding to the gloom about the state of adulthood in this country.

Twenge's findings are much less alarming than Deaton and Case's but they're still pretty glum. It appears Americans in their 30s are becoming less happy.

Happier teens, sadder adults

She explains her research in a recent piece in The Atlantic: "To examine long-term trends in happiness in the U.S., my colleagues and I merged reams of survey data from 1972 to 2014, from four nationally representative samples totaling 1.3 million Americans. All were between the ages of 13 and 96, and all were asked the same standard question on general happiness: 'Would you say that you are very happy, pretty happy, or not too happy?'"

Here's the upside of the results -- teenagers are even happier than they used to be (and based on popular culture at least, your teenage years have always been kind of a blast so that's saying something) -- but the rest of the findings were less cheerful. Adulthood, apparently, isn't what it used to be.

"Past research has found that people grow steadily happier as they age from adolescence to older adulthood, with happiness peaking when people reach their 60s and 70s; the moodiness of youth subsides, and maturity brings more contentment. But our analysis found that this was no longer true: In the last five years, the once-reliable correlation between age and happiness among adults has vanished. Adults 30 and over are less happy than they used to be," Twenge writes.

Why?

Twenge offers a couple of possible explanations for the trend though no one is sure what's causing the downturn in adult happiness. One possible culprit is just our expectations. Many of the generation now entering their 30s (the so-called millennials) were raised to believe they were all special flowers who could achieve great and exciting things. If that's your understanding of adulthood, endless laundry and a nine-to-five job is sure to be a comedown.

This hypothesis jives with popular culture and generalized anxieties about coddled kids Here's one entertaining post, which recently did the rounds online, that agrees with the idea that our expectations are to blame for our misery.

Twenge also offers another possible explanation though -- more social isolation. "Indicators of individualism," she writes, "are all higher now in the U.S. than in previous decades. Stable relationships are on the decline, with fewer marriages and less community involvement. Individualism works well for young people, who are often unattached and working on finding themselves--adolescence and young adulthood are inherently self-focused life stages. But for those moving into later stages of life, individualism fails to provide the ingredients for happiness in the same way."

Why do you think reported happiness levels among 30-somethings are falling?