Some drug addicts more likely to relapse than others: Study

But, the older the person with drug abuse issues, the more likely they will not relapse from treatment.

"We can improve our tailoring of treatment to each patient if we know who among patients taking methadone treatment is at high risk for opioid relapse," said Dr. Zena Samaan, principal author of the study and an associate professor of psychiatry and behavioural neurosciences of McMaster's Michael G. DeGroote School of Medicine.

"As well, health care providers can target more aggressive therapies to those at high risk."

Canada and the U.S. are the world's highest consumers of prescription opioids which are common drugs for pain management. At least one study says one in six Canadians using prescription opioids. But these medications are also highly addicting and liable for abuse. Methadone maintenance treatment is the most common intervention for those with drug addiction, but relapse is common, with 46% of patients continuing to use illicit opioids during or after the methadone treatment.

"Since opioid disorder is chronic, remitting and relapsing, we wanted to find those factors that led to longer abstinence from illicit opioids," said Leen Naji, a student of McMaster's Michael G. DeGroote School of Medicine and first author of the paper. "There has been little research on this issue of how long a patient can go without the illicit opioid use."

Samaan and her team looked at 250 adults who had been on a methadone treatment for an average of four years at 13 clinical sites in Ontario.

They found that:

* Those who injected drugs were more than twice as likely to relapse by using opioids while on treatment, than those who did not inject drugs;

* For every year increase in age of starting to abuse opioids there is a 10% increase in relapse;

* For every day of benzodiazepine use in the previous month there is a 7% increase in relapse; while current age carries 7% reduction in risk of relapse (the older the person, the less likely of relapse).

The study was published by the Substance Abuse Research and Treatment journal and was funded by the Canadian Institutes of Health Research, the McMaster Population Genomics Program and the Peter Boris Centre for Addiction Research.