Washington, Feb 27 (IANS): Driven primarily by financial difficulties, suicide rates for adults between 40 and 64 years of age in the US have risen about 40 percent since 1999, with a sharp rise since 2007, says a study.

Economic factors were present in 37.5 percent of all suicides in 2010, rising from 32.9 percent in 2005, the findings showed.

"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," noted one of the study authors Katherine Hempstead from Rutgers University.

One possible explanation could be the detrimental effects of the economic downturn of 2007-2009, leading to disproportionate effects on house values, household finances and retirement savings for that age group.

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

"External circumstances have also increased in importance among those aged 65 years. Financial difficulties related to the loss of retirement savings in the stock market crash may explain some of this trend," Hempstead pointed out.

Using data from the National Violent Death Reporting System (NVDRS), researchers were able to analyse 17 distinct suicide circumstances and four indicators related to planning and intent.

The suicide circumstances were grouped into three major categories: personal, interpersonal and external.

Examples of personal circumstances are depressed mood, current treatment for a mental health problem or alcohol dependence.

Interpersonal circumstances include an intimate partner problem, the death of a friend or being a victim of intimate partner violence.

Examples of external circumstances are a job or financial problem, legal problem or difficulty in school.

The study appeared in the American Journal of Preventive Medicine.