Stimulants use such as cocaine and amphetamine is associated with a nearly two-fold greater likelihood of suicidal behaviour amongst people who inject drugs, say researchers at the University of Montreal and the CHUM Research Centre. Drug addiction had already been identified as a major risk factor for suicide, and it is in fact the cause of ten percent of deaths among drug users. The data from this groundbreaking study could help develop and evaluate more appropriate suicide prevention efforts in this highly vulnerable population.

The researchers were able to explore the relationship between substance abuse and risk of suicidal behaviour by studying in detail the different types of substances used among more than 1,200 people who inject drugs (PWIDs). "We know that substance use is associated with the risk of suicide attempt and completed suicide. However, there are many different profiles of drug users. The data available until recently did not allow identifying the substance use patterns most at risk. We wanted to know who among substance users were actually more likely to attempt suicide," said Didier Jutras-Aswad, a professor in the Department of Psychiatry at the University of Montréal and researcher at the CHUM Research Centre.

To do this, they used data from the HEPCO Cohort to examine the individual and contextual factors associated with hepatitis C infection. This cohort is a longitudinal study from the "Saint-Luc Cohort" research program that was conducted in 2004 by Dr. Julie Bruneau, a researcher at the CRCHUM and professor in the Department of Family Health at the University of Montreal. The HEPCO cohort participants were 18 or older and had injected drugs in the past six months. Twice a year, the participants in the study completed a questionnaire to better understand their drug use habits and assess certain markers of mental health. The median follow-up was four visits. They were specifically asked if they had attempted suicide in the past six months, but also about the nature and frequency of their consumption. Several substances were evaluated in detail, including cocaine, amphetamines, opioids, cannabis, alcohol, and sedative-hypnotics available illegally on the street (i.e., barbiturates and benzodiazepines).

Their findings indicate that suicide attempts are most common among PWIDs. At the beginning of the study, nearly 6% of participants had indeed reported a suicide attempt in the previous six months, a dramatically higher rate than the general population. During follow-up, 143 participants experienced at least one episode of attempted suicide. The researchers found that chronic and occasional use of stimulant drugs such as cocaine and amphetamines was associated with nearly two-fold greater odds of reporting an attempt than the use of other drugs to report a suicide attempt. Surprisingly, however, they did not observe the same positive association with other substances, including opiates, which are nevertheless regarded as among the most damaging to health and psycho-social wellbeing.

So why this difference between stimulant and opiate drugs? According to the researchers, a set of neurobiological, behavioural and social differences between stimulant users and opiate users could explain these findings. Stimulant users are more vulnerable because they are more impulsive and characterized by changing moods. The researchers also point out that cocaine addiction treatments are virtually nonexistent - drug treatment programs are often structured around opiates or alcohol.

"Our study addresses a number of important issues that could change practice. While it confirms that drug use itself represents a significant risk for suicidal behaviour, it identifies cocaine and amphetamine users as a higher-risk population. We therefore need to develop more effective intervention and prevention programs tailored to this target population. It would also seem essential to carry out further research with particular emphasis on a more detailed assessment of mental health and its interaction with drug use over time," said Jutras-Aswad.

###

About the study: Andreea Adelina Artenie, Julie Bruneau, Geng Zang, François Lespérance, Johanne Renaud, Joël Tremblay, and Didier Jutras-Aswad published the article "Associations of substance use patterns with attempted suicide among persons who inject drugs: Can distinct use patterns play a role?" on November 26, 2014, in the journal Drug and Alcohol Dependence (online publication).

The University of Montreal is officially known as Université de Montréal.