Suicide rates among middle-aged Americans have climbed by nearly 40 percent since 1999, and a study published Friday in the American Journal of Preventive Medicine links that uptick to the economic downturn of 2007 to 2009.

"Relative to other age groups, a larger and increasing proportion of middle-aged suicides have circumstances associated with job, financial, or legal distress and are completed using suffocation," study authors Katherine A. Hempstead, PhD, director of the Robert Wood Johnson Foundation, in Princeton, N.J., and the Center for State Health Policy at Rutgers University, and Julie A. Phillips, of the Institute for Health, Health Care Policy and Aging Research, in New Brunswick, N.J., noted in a news release.

Researchers found that external economic factors were present in nearly 38 percent of all completed suicides in 2010, compared to 32.9 percent in 2005, according to a news release. The number of suicides using suffocation— a method shown to be common in suicides related to financial stress— increased by nearly 60 percent among those aged 40 to 64 years between 2005 and 2010, while those aged 15 to 39 saw an 18 percent rise and those over age 65 saw a 27.2 percent increase in suicide rates. Financial worry linked to loss in retirement savings may explain the increased suicide rate among older adults, researchers said.

"The sharpest increase in external circumstances appears to be temporally related to the worst years of the Great Recession, consistent with other work showing a link between deteriorating economic conditions and suicide,” researchers wrote.

Study authors drew data from the National Violent Death Reporting System (NVDRS), which includes information on violent deaths from medical examiner and coroner reports, toxicology reports, law enforcement records, death certificates and the like. They used these documents to pinpoint 17 different suicide circumstances and four indicators related to planning and intent.

Researchers called for greater awareness that various financial setbacks can be a risk factor for suicide, and urged employee assistance programs, as well as human resource departments and credit counselors to be on the lookout for at-risk people and make referrals accordingly, according to the news release.

“Increasing access to crisis counseling and other mental health services on an emergency basis— as is often provided at times of natural disaster— should also be considered in the context of economic crises,” the study authors said.