Mac study pegs cannabis as potential predictor of relapse for female methadone patients

Molly Hayes 

Marijuana use could be a predictor for relapse among women undergoing opioid addiction treatment, a Hamilton study has found. 

A research team from McMaster University and St. Joseph's Healthcare Hamilton recruited 777 participants from Canadian Addiction Treatment Centre sites across the province as part of an ongoing research file into the risk factors of addiction. 

About 60 per cent of men and 44 per cent of women in methadone treatment therapy also use cannabis, the study found. The women who smoked pot, the study found, were 82 per cent more likely to relapse and use opioids. 

Senior study author Zena Samaan — an associate professor of psychiatry and behavioural neurosciences at McMaster University and a clinician and researcher at St. Joseph's Healthcare — says there are multiple hypotheses as to why women seem to be affected differently than men. 

"We also found that the women in this sample have more psychological and physical health problems compared to men. We see the impact of the (cannabis) on them much worse." 

On the eve of marijuana legalization, Samaan says these findings come at an especially important time. 

"We want to add to the argument that cannabis is not harmless, despite the belief that it is a natural substance," she said. 

"One (of the concerns it raises) is that, if women continue to use cannabis, they're not going to do well in treatment. So what are we doing? We need to address that specifically."

A major recommendation of the study is that methadone clinicians screen for marijuana use on top of opioid use — something she says used to be done, but was largely scrapped due to resource limitations. 

The study also highlights a need for more comprehensive and personalized addictions and mental-health care, she says, noting that roughly 80 per cent of the study participants identified as having mental health issues. 

In 2014-2015, according to statistics from the province's Ministry of Health and Long Term Care, 54,000 people across Ontario were on methadone treatment. 

The Canadian Centre on Substance Abuse reports that opioid-related deaths increased by more than 240 per cent between 1990 and 2010. 

More than 700 people died of opioid-related deaths in Ontario in 2015.