CHICAGO, Oct. 25 (Xinhua) -- A study from the University of Michigan (UM) and Dartmouth University found that in an adjusted analysis, U.S.-born residents were more than five times likely to use prescription opioids than new immigrants.

Immigrants who lived in the United States between five and 15 years were more than three times as likely to use opioids than new immigrants, and those who lived in the country longer than 15 years were four times likelier to use opioids than new immigrants.

Using data from the national Medical Expenditure Panel Survey, the researchers examined the influence of American culture on opioid use among the estimated 42 million adult immigrants. Nearly 8 percent of immigrants use prescription opioids, compared to 16 percent of adults born in the United States.

"Our results indicate that American culture has a potent influence on opioid prescribing, as evidenced by the dramatic time effect that is associated with a massive increase in prescription opioid use among immigrants to the United States," said Matthew Davis, associate professor at the UM's School of Nursing and Medical School.

This uptick happened despite controlling for pain levels, health care access and income.

Increased opioid use with longer duration in the United States provides stronger evidence of a unique American culture that promotes opioid use, the researchers said.

Although the study didn't explicitly identify assimilation into American culture, the researchers suspect the adoption of American attitudes and culture likely influences the dynamic between health care providers and immigrant patients.

Policy efforts to decrease opioid reliance would potentially benefit from acknowledgment of unique American cultural factors that influence opioid use, the researchers said.

The study was published online in JAMA Network Open on Friday.