Simultaneous cocaine and alcohol use has been linked to an increase in suicide risk, according to a new study.
The study of hundreds of suicidal emergency department (ED) patients from around the US 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, researchers said.
"One unexpected finding was that, when examined independently, alcohol use had no significant association and cocaine use had a borderline significant association," researchers said.
"However, reporting both alcohol misuse and cocaine use was significantly associated with a future suicide attempt," they said.
Led by Sarah Arias, assistant professor at 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, patients received an experimental intervention. Researchers gathered demographic and substance use information from the participants and then followed them for a full year afterwards.
The key outcome in the 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 and her colleagues found was that although people in the study reported misusing many different substances, including marijuana, prescription painkillers, tranquilisers 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 said. 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 emphasise the complex interaction of sex, substance use, and suicide attempts," Arias said.
The study was published in the journal Crisis.
