Women are more likely to develop an opioid addiction from prescribed painkillers, according to a recent study.

Researchers from McMaster University found that painkillers prescribed by doctors are the starting point for an opioid addiction for more than half of female methadone clinic patients, and they need different treatment from men with addiction. The study reveals that more than half of women and a third (38%) of men reported doctor-prescribed painkillers as their first contact with opioid drugs, a family of drugs which include prescription medicines such OxyContin and codeine, as well as illicit drugs such as heroin.

"Most methadone treatment is based on studies with few or no women at all. We found men and women who are addicted to opioids have very different demographics and health needs, and we need to better reflect this in the treatment options that are available," Monica Bawor, first author of the paper, said in a statement.

For the study, researchers collected and analyzed data from more than 500 people attending 13 Ontario methadone clinics in Canada. They provided detailed information on their health and lifestyle, as well as urine tests for drug use.

Compared to men, women were found to have more physical and psychological health problems, more childcare responsibilities, and were more likely to have a family history of psychiatric illness. Men were more likely than women to be working and more likely to smoke cigarettes. Rates of cannabis use were relatively high (47%) among both men and women.

"A rising number of women are seeking treatment for opioid addiction in Canada and other countries yet, in many cases, treatment is still geared towards a patient profile that is decades out of date -- predominantly young men injecting heroin, and with few family or employment responsibilities," Bawor said.

The study highlights the changing profile of people addicted to opioids. Compared to results from studies in the 1990s, the average age of patients being treated for opioid addiction is older (38 compared to 25 years), with opioid use starting at a later age (25 rather than 21 years). Injecting drug use has reduced by 60 percent, and there has been a 50 percent reduction in rates of HIV in opioid users as a result.

At the same time, there has been a 30 percent increase in the number of patients becoming addicted to opioids through doctor-prescribed painkillers, usually for chronic pain management.

The findings are detailed in the journal Biology of Sex Differences.