People with no more than a high school education may be less likely to die by suicide when minimum wages rise, a new study suggests.

Researchers examined the difference between state and federal minimum hourly wages as well as state unemployment and suicide rates for adults 18 to 64 years old between 1990 and 2015.

Nationwide, there were 478 changes in state minimum wages during the study period. The difference in annual wages for full-time workers in states with the federally established minimum wage and workers in states with higher minimum wages averaged $2,200.

Each $1 increase in minimum wage was associated with 3.5 percent to six percent decreases in suicide rates among adults without education beyond high school, researchers calculated.

Minimum wage hikes didn't appear to impact suicide rates for people with more education, however.

Nancy Pelosi is among the Democrats who support raising the federal minimum wage to $15. New research suggests that doing may help reduce suicide rates in the US

'Minimum wage laws can potentially intervene in the wealth-health relationship to improve wellbeing of those working at low-wage jobs and their dependents, who have less access to resources and are at higher risk of depression and suicide,' said lead study author John Kaufman of the Rollins School of Public Health at Emory University in Atlanta.

'Given the persistent social stigmas associated with mental health issues in the US. and elsewhere, we need to realize that upstream societal factors affect mental health,' Kaufman said by email.

'It is likely more effective to make upstream changes to improve health, rather than leaving it up to individuals struggling with depression and suicidal thoughts and their families or friends to navigate on their own.'

Suicide rates have long been higher in low-income households than among more affluent people, previous research suggests.

Raising the minimum wage has been linked to a number of positive outcomes for low-income Americans including higher odds of graduating high school and lower odds of having unmet medical needs.

At the start of the study in 1990, 36 states had a minimum wage equal to the federal rate; by 2015, this had fallen to 21 states, according to the report in the Journal of Epidemiology and Community Health.

Between 1990 and 2015, the study found, 399,206 people with a high school education or less took their own lives compared with 140,176 people with a college degree or more.

The impact of minimum wage increases on suicide rates among less-educated Americans was most pronounced during periods of high unemployment.

'Minimum wage laws may be especially important during periods of high unemployment when employers have an incentive to lower wages, which can increase financial stress on workers,' said Alex Gertner, a researcher at the Gillings School of Global Public Health at the University of North Carolina, Chapel Hill, who wasn't involved in the study.

'Minimum wages laws may also help keep wages higher during economic downturns so that workers can help unemployed friends and family members,' Gertner said by email.

After the 2009 peak in unemployment following the financial crash, 13,800 suicides could have been prevented between 2009 and 2015 among less-educated working-age adults with a $1 increase in the hourly minimum wage, researchers calculated. A $2 increase could have prevented 25,900 suicides during this period, they estimate.

Over the entire 26-year period, the researchers estimated that a $1 increase in the hourly minimum wage could have avoided 27,550 suicides in this group of workers, while a $2 increase could have prevented 57,350 suicides.

The study wasn't a controlled experiment designed to prove whether or how wages might directly impact mental health or suicide rates.

Still, the results add to evidence that economic policies can directly affect health and longevity, said Martin McKee, a researcher at the London School of Hygiene and Tropical Medicine in the UK who wasn't involved in the study.

'There is a widespread narrative, especially in the US, that everyone is responsible for looking after themselves,' McKee said by email.

'This study, taken with the other evidence, provides a strong argument for legislation to protect workers who are too easily exploited by unscrupulous employers.'