PROVIDENCE, R.I. [Brown University] —In a general sense, medical studies support the popular intuition — a staple of movies and literature — that suicidal behavior and substance misuse are linked. But the relationship between the two is not so simple. A new study of hundreds of suicidal emergency department (ED) patients from around the U.S. found that the significance of the link varied with age, gender and race. Across the board, however, the use of cocaine and alcohol together was a red flag.

“One unexpected finding was that, when examined independently, alcohol use had no significant association and cocaine use had a borderline significant association,” wrote authors of the study in the journal Crisis. “However, reporting both alcohol misuse and cocaine use was significantly associated with a future suicide attempt.”

Led by Sarah Arias, assistant professor (research) of psychiatry and human behavior in the Alpert Medical School of Brown University, the team examined 874 men and women who presented at one of eight emergency departments around the country between 2010 and 2012. The patients were participants in the Emergency Department Safety Assessment and Follow-up Evaluation study, led by the University of Massachusetts Medical School. Individuals included in the analysis received standard care and either reported a recent suicide attempt or were actively engaged in suicidal thoughts at the time of the initial ED visit. In another arm of the study, not included in this analysis, patients received an experimental intervention. Researchers gathered demographic and substance use information from the participants and then followed them for a full year afterward.

The key outcome in Arias’ new study was whether people attempted suicide in the year following the ED visit. Of the 874 people, 195 people did at least once.

What Arias, who is also a research psychologist at Butler Hospital, and her colleagues found was that although people in the study reported misusing many different substances, including marijuana, prescription painkillers, tranquilizers and stimulants, only cocaine and alcohol appeared to have a significant association with suicide risk. Of the entire study population, 298 misused alcohol, 72 were using cocaine and 41 were using both. Specifically, of those using both, the chance of attempting suicide again was 2.4 times greater than among people in the study who were not.

They also found that substance misuse was less likely an indicator of suicide risk among whites and women. Older people, meanwhile, were more likely to have an association between substance misuse and suicide.

Women are not less likely to be suicidal, the researchers note. In fact, they were more likely than men to have reported prior attempts. But the data showed that substance abuse was less likely to be involved among women.

“These disparate findings emphasize the complex interaction of sex, substance use, and suicide attempts,” Arias and her co-authors wrote. “They also suggest women may be differentially at risk depending on whether they report substance use or past suicide attempts.”

The study does not say anything about whether substance abuse causes suicidal behavior because it only reports observations of associations. But Arias said she hopes the data will advance the understanding of how misuse of particular substances, among particular patients, may affect their risk of suicide.

“It’s not a clear-cut, straightforward association,” Arias said. “Even though substance use is often touted as a very strong predictor of suicidal intentions and behaviors, when we look at individual substances we’re seeing that there’s not that consistency in the future association with behavior.”

Figuring out the specific cases where substance misuse is predictive could help save lives.

“We’re on our way to trying to identify factors that can be used to better assess and identify people who are at risk for suicide, and ultimately I think this is a step in the right direction to get a better picture,” she said. “Patients who have potentially comorbid alcohol and cocaine use may be at a higher risk. Findings like these can be useful for informing suicide risk assessment.”

In addition to Arias, the study’s other authors are Orianne Dumas, Ashley Sullivan, Edwin Boudreaux, Ivan Miller and Carlos Camargo Jr.

The research was funded by the National Institute of Mental Health (grant: U01MH088278).