Study looks at connection between mental illness, opioid addiction

As the country reels under the spread of opioid addiction and overdosing, a recent study conducted by Dartmouth-Hitchcock and the University of Michigan has brought a new focus to a possible connection between mental illness and addiction.

According to the study, the rate of opioid prescriptions in the United States has quadrupled in the past 15 years. The researchers found that more than half of all prescriptions for opioids in the U.S. each year are given to Americans with two of the most prevalent mental health disorders.

That means that 60 million of 115 million prescriptions for opioids distributed go to a portion of society that only accounts for 16 percent of the total U.S. population. These are prescriptions and do not necessarily lead to addiction, but the numbers are still alarming given that mental health disorders often correlate with substance abuse.

“The premise for the study came from clinical observations made by my co-author Brian Sites, M.D., at Dartmouth-Hitchcock,” said study co-author Matthew Davis, MPH, Ph.D., a health services researcher, assistant professor at the University of Michigan School of Nursing, and adjunct assistant professor at the Geisel School of Medicine at Dartmouth and the Dartmouth Institute for Health Policy and Clinical Practice.

“There has been work done in smaller studies on the connection between mental health disorders and pain but this is the first national study to look at the issue with opioid use.”

Even when looking at specific subgroups, he explained, including those with chronic pain or cancer, mental health disorders are still strongly correlated with opioid use.

“We still see that Americans with mental health disorders had a higher use,” Davis said.

The study looked at a sample of adults taken from the Agency for Healthcare Research and Quality’s 2011 and 2013 Medical Expenditure Panel Surveys, a survey of the non institutionalized U.S. population.

The researchers examined the relationship between anxiety and depression, the two most common mental health disorders  and prescription opioid use as defined by receiving at least two prescriptions in a calendar year.

They found that of the 38.6 million Americans who have mental health disorders, nearly 19 percent of them use prescription opioids. And, as stated above, more than half of all total prescriptions in the U.S. go to this group.

The study, while informative, leaves many questions unanswered. How many of these people, for instance, go on to become addicted to the medication or leave prescription medication in favor of illegal substances? How many actually take all the medication they are prescribed? The correlation between the two is also difficult to tease out from these results.

Future studies may need to first identify people with mental health disorders and then track them over time to see rates of opioid use to better understand the correlation.

“More work needs to be done to understand the interaction between mental health and pain,” Davis said. “There are a number of teams around the country looking at the relationships between mental health and pain and opioid use now and over time we hope to understand more about what comes first.”

The biggest questions, Davis admits, are not answered by this one study but that does not lessen the impact of the work.

“From our perspective,” he said, “we have to start somewhere with reducing the nation’s dependency on prescription opioids. It is important for providers who take care of these people to be aware of the risks. Our study suggests that the population of Americans with mental health disorders is a good place to begin.”