People who are too smart for their jobs are putting themselves at risk of depression, according to a new study.
The study looked at information from more than 16,600 employed people aged between 25 and 61 from 21 countries around Europe.
Researchers measured participants' level of depression based on a survey.
They found those who were "over-educated" - had more years of study than their job required - were at increased risk of mental illness.
This could be because they aren't stimulated by their jobs and can't use all their acquired skills, said researcher Prof Piet Bracke, a sociology expert from Ghent University in Belgium.
These employees also have less status and prestige and tend to have unbalanced support networks (rely on others more than other rely on them), which could compound the problem, Prof Brake told the website, LiveScience.
Having a number of highly educated people in the one country can have a negative effect on the mental health of the entire population. In countries where more education did not provide significantly more job security or salary, even those with degrees who had jobs that matched their skill level saw declines in their mental health on average, Prof Bracke said.
"If the economic returns of education decrease, it affects the mental health of all the well-educated," he explained.
However, Prof Brake made it clear that he was not discouraging higher education.
"At the country level, if the number of people with university education continues to rise, [and] if there isn't an equivalent upgrading of the labor market, it will deteriorate the mental health of the population."
While people may start out with a job that they are overqualified for in the beginning of their career, they need opportunities to move upward in their field within a few years, or they could experience declines in mental health, he said.
The findings were revealed this week at the American Sociological Association meeting.