Analyzing data from 6.9 million adolescents and adults from all over the country, Twenge found that Americans now report more psychosomatic symptoms of depression, such as trouble sleeping and trouble concentrating, than their counterparts in the 1980s.

"Previous studies found that more people have been treated for depression in recent years, but that could be due to more awareness and less stigma," said Twenge, the author of "Generation Me: Why Today's Young Americans are More Confident, Assertive, Entitled -- and More Miserable than Ever Before." "This study shows an increase in symptoms most people don't even know are connected to depression, which suggests adolescents and adults really are suffering more."

Compared to their 1980s counterparts, teens in the 2010s are 38 percent more likely to have trouble remembering, 74 percent more likely to have trouble sleeping and twice as likely to have seen a professional for mental health issues. College students surveyed were 50 percent more likely to say they feel overwhelmed, and adults were more likely to say their sleep was restless, they had poor appetite and everything was an effort -- all classic psychosomatic symptoms of depression.

"Despite all of these symptoms, people are not any more likely to say they are depressed when asked directly, again suggesting that the rise is not based on people being more willing to admit depression," said Twenge.

The study also found that the suicide rate for teens decreased, though the decline was small compared to the increase in symptoms of depression. With the use of anti-depressant medications doubling over this time period, Twenge speculates that medication may have helped those with the most severe problems but has not reduced increases in other symptoms that, she says, can still cause significant issues.

Twenge's findings were published in the journal Social Indicators Research, and an updated and revised edition of "Generation Me" is being released today.

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Journal Reference:

1. Jean M. Twenge. Time Period and Birth Cohort Differences in Depressive Symptoms in the U.S., 1982–2013. Social Indicators Research, 2014; DOI: 10.1007/s11205-014-0647-1