Suicide attempts by young adults, particularly those with mental illness and less education, are increasing, a new study concludes.

Older adults have the highest overall suicide rates in the United States, the researchers report in JAMA Psychiatry. The findings come from surveys of more than 69,000 adults, according to HealthDay.

Between 2004 and 2014, the annual suicide rate increased from 11 percent to 13 percent per 100,000 people. While middle-aged adults (aged 45-64 years) had the highest suicide rate, young adults (aged 21-34 years) had the biggest increase in suicide attempts.

Lead researcher Dr. Mark Olfson of Columbia University Medical Center said it is not clear why suicide attempts appear to be increasing among young adults.

“It is possible that these trends are partially explained by the effects of the recent Great Recession,” he said. “Younger adults and adults with less education may have been especially hard hit by the recession in terms of economic and psychological stress. Unemployed adults, those with less education, and adults with lower family incomes were all particularly likely to report a recent suicide attempt.”