Lead author Brandon Marshall -- a postdoctoral fellow at the Mailman School of Public Health in New York and research coordinator for the Urban Health Research Initiative in British Colombia -- and colleagues said the causal pathway between injecting methamphetamine and suicidal behavior requires further investigation, but it likely involves a combination of neurobiological, social, and structural mechanisms.
"Compared to other injection drug users, it is possible that methamphetamine users are more isolated and have poorer social support systems," Marshall said in a statement. "The high rate of attempted suicide observed in this study suggests that suicide prevention efforts should be an integral part of substance abuse treatment programs."
The seven-year study, which ended in May 2008, involved 1,873 participants -- median age 31 -- from an area of Vancouver known as a center for illicit drug use where fatalities from drug overdoses and drug-related violence are common.
More than 36.2 percent of participants were female, and 32.1 percent were of Aboriginal ancestry. Eight percent reported a suicide attempt.
"This is one of North America's largest cohorts of injection drug users, and the research is among the first longitudinal studies to examine attempts of suicide by injection drug users," Marshall said in a statement.
The study was published in the journal Drug and Alcohol Dependence.
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