Effectiveness of an opioid agonist treatment program on suicide prevention in NSW

What's the issue?

Some population groups are identified as having an increased risk of suicide. People who use alcohol and other drugs are one such group, with those living with opioid use disorder (OUD) having almost eight times the risk of suicide-related death compared to the general population.¹ Globally, there are an estimated 40.5 million people with OUD.

Deaths due to opioid use can be difficult to classify, as it can be hard to determine if the death was an accidental overdose or had suicidal intent. Prevention of accidental overdose and suicide require different approaches, treatments and supports. Recent approaches to suicide prevention suggests a shift from focusing on an individual level, to exploring population-based prevention approaches. Population-level interventions tend to focus on increasing protective factors for suicide, and address community-wide risk factors, or broad risk factors identified for certain population groups. Population-level interventions include activities with wide coverage such as means restriction.

Opioid receptors influence the body’s perception of pain and are part of the body’s normal response to hormones, drugs and neurotransmitters. Opioid antagonists are medications that block the effects of opioids.

Opioid agonist treatment (OAT), using opioid substitutes such as methadone and buprenorphine, is an effective population-level treatment for OUD reducing the risk of multiple causes of death, including suicide.

A 2021 meta-analysis of 14 studies and more than 175,000 people with OUD found that OAT reduces the risk of suicide-related mortality by more than half.²

Research in Australia and the United Kingdom found that extended periods of OAT are associated with significantly lower risks of self-harm and suicide at the individual level, however the impact of OAT at a wider population level is unknown.

In 2021, Chaillon et al. developed a model to assess the impact of the NSW OAT program on overdose and other-cause mortality from 2001 to 2020. Chaillon et al.’s model estimated that the NSW OAT program averted over 4,000 deaths between 2001 and 2020, preventing 53% of overdose deaths and 27% of deaths from other causes.

The researchers of this paper expanded on the work of Chaillon et al. to estimate the impact of OAT on suicide-related deaths among people who have received OAT in NSW.

What was done?

Researchers examined data of people engaged in OAT between 2001 and 2017 in NSW, Australia. The data was collected from the Controlled Drugs Data Collection (CoDDaC) and shows when people were engaged with OAT and when they had periods of not engaging in both community and corrections settings.

The number of suicides for people engaged or not engaged with OAT in both corrections and community settings was extracted.

Researchers then used this data to model scenarios to predict the number of suicide deaths that were prevented due to OAT.

What was found?

The study data showed that:

• There were 46,845 individuals prescribed OAT in NSW between 2001-2017.
• Of those prescribed OAT, 67.7% were male. The median age was 32 years old.
• An average of 20,930 people received OAT per year.
• Between 2001 and 2017, there were 433 suicides.
• Of suicide deaths, 420 occurred in the community and 13 in corrections facilities.
• The ratio of suicide deaths was slightly higher in corrections facilities compared to community settings.

Modelling of OAT engagement and prevention of suicide:

• Among individuals engaged OAT in NSW between 2001-2017, the model estimated that 153 suicides occurred among individuals on OAT, whereas 446 suicides occurred among those not receiving OAT.
• In corrections settings, the model estimated the number of suicides among those on OAT was five, and 22 suicides in those not those not receiving OAT.
• The researchers found OAT was linked to a prevention of 2% of all suicides of the 15,388 that occurred in NSW during 2001-2017.

The researchers used the model to predict suicide rates without any OAT as an intervention, with the model showing 39 suicides in corrections and 924 in the community (a total of 963 deaths by suicide).

The modelling showed the OAT program was estimated to have prevented 338 suicides between 2001 and 2020.

*The researchers acknowledge the potential suicides prevented may be inaccurate due to limitations of the modelling and availability of data.

Why are the findings important?

Modelling can demonstrate the potential impact of population-level public health interventions for suicide. The modelling showed that OAT prevented 35% of suicide deaths in community settings, and 27% of suicide deaths in corrections settings within the study period.

Although these findings are specific to OAT in NSW, similar modelling in other Australian states and territories may show potential prevention of suicide attributed to OAT.

Given that OUD is often linked to other risk factors increasing suicide risk such as homelessness, engagement with OAT may have some ‘protective’ effect against other risk factors.

Further research and modelling of OAT and suicide prevention in different settings, and internationally is encouraged to determine the Australian specific and global impact of OAT as a population-based suicide prevention approach.