Suicide attempts and non-fatal opioid overdose have been examined among opioid-dependent individuals in a number of different studies, with some disagreement on whether they are distinct behaviours. These studies however, rarely include an exhaustive list of correlates associated with either behaviour. Additionally, only one study has compared the two behaviours using mutually exclusive categories (Rossow & Lauritzen, 1999
). Overall, the present study found distinct correlates for suicide attempts and non-fatal opioid overdose.
The correlates identified for non-fatal opioid overdose were consistent with the literature. Older, more experienced heroin users were identified as more at risk of opioid overdose (Darke & Hall, 2003
; Gossop, Griffiths, Powis, Williamson, & Strang, 1996
). Additionally, injecting opioids (as opposed to using other routes of administration) was associated with increased overdose risk (Bennett & Higgins, 1999
; Darke & Hall, 2003
; Gossop, Stewart, Treacy, & Marsden, 2002
; Stewart, Gossop, & Marsden, 2002
High impulsivity was also identified as a unique risk factor for non-fatal opioid overdose. The research supporting this finding, however, is limited. In fact more research actually supports a relationship between impulsivity and suicide attempts (Dougherty et al., 2004
), which was not identified in this study. It is possible that this discrepancy relates to the type and nature of impulsivity assessed in the current study. The BIS is a self-report measure and as such typically measures lifelong “trait” aspects of impulsivity which generally do not take into account any “state-dependent” fluctuations in impulsivity (include experiencing stress, loss or anxiety), which may lead to attempted suicide (Fawcett, 2001
; Moeller, Barratt, Dougherty, Schmitz, & Swann, 2001
). Additionally, individuals with impulsive personality traits tend to seek immediate rewards (Kirby, Petry, & Bickel, 1999
). Polydrug use or drug use immediately post release from prison could be considered to be impulsive behaviours, and have both been identified as correlates for non-fatal opioid overdose among other studies (Darke & Hall, 2003
). Considering this, it is not surprising that high impulsivity was identified as a unique risk factor for non-fatal opioid overdose in this study.
Sedative dependence was also identified as a risk factor for non-fatal opioid overdose. Studies have consistently found that both fatal and non-fatal opioid overdoses often occur with the consumption of other drugs, particularly benzodiazepines and alcohol (Gossop et al., 2002
; White & Irvine, 1999
). Sedatives appear to be a proximal risk factor for non-fatal overdose as they act as a central nervous system depressant, similarly to opioids (Darke et al., 2006
). Additionally, studies have identified polydrug dependence as a marker for comorbid psychiatric diagnoses (Darke & Ross, 1997
). It was not possible, however, in this study to determine if the indexed overdose occurred in conjunction with drugs other than opioids.
In agreement with the findings of other studies, it seems that it is possible to differentiate between attempted suicide and non-fatal opioid overdose (Ravndal & Vaglum, 1999
). Depression, anxiety disorders, and personality disorders were associated with suicide attempts, whereas drug use variables were associated with non-fatal opioid overdose such as injecting opioids and sedative dependence. A previously published paper on this sample found that the use of opioids (particularly heroin) to attempt suicide is atypical among opioid users (Maloney et al., 2007
), which is consistent with the literature (Darke & Ross, 2001
; Johnsson & Fridell, 1997
; Vingoe et al., 1999
). In fact, as mentioned previously, the most commonly reported method for attempting suicide among opioid users is an overdose on benzodiazepines (Darke & Ross, 2001
; Maloney et al., 2007
). These findings highlight that reported suicide attempts are not misclassified opioid overdoses. We also found that opioid-dependent individuals who reported a lifetime suicide attempt reported high levels of suicidal intent on each measure used. Taken together, these results strengthen the conclusion that opioid-dependent individuals have the capacity to differentiate and report separately on the two behaviours (Maloney et al., 2007
). Additionally, a considerable proportion of the sample reported both behaviours, which is consistent with previous research (Darke & Ross, 2001
; Rossow & Lauritzen, 1999
; Vingoe et al., 1999
). This suggests that although they may be distinct behaviours, they may not apply to separate sub-groups of opioid-dependent individuals.
A number of correlates for suicide attempts were identified among this sample. Consistent with previous research, experiencing a major depressive episode, being female and screening BPD+ were identified as being associated with a history of suicide attempts (Darke & Ross, 2001
; Darke et al., 2004
; Murphy et al., 1983
; Roy, 2002
). Meeting criteria for an anxiety disorder (either PTSD or panic disorder) was also associated with a history of attempted suicide only. Although research has linked PTSD and attempted suicide among the general population (Sareen, Houlahan, Cox, & Asmundson, 2005
), and among opioid dependent individuals (Darke et al., 2004
), the literature examining panic disorder as a risk factor for suicide attempts among opioid-dependent individuals is limited. Studies among the general population have found that panic disorder increases an individual’s risk of attempting suicide (Pilowsky, Wu, & Anthony, 1999
; Pirkis, Burgess, & Dunt, 2000
; Schmidt, Woolaway-Bickel, & Bates, 2001
). Considering the findings of this study, research should address how the findings of previous research may translate to opioid-dependent individuals.
This study also found that participants with a history of both non-fatal overdose and attempted suicide were characterised by a more complex clinical profile, which included drug use behaviours, psychological problems, and a history of childhood trauma. Although the literature in this area is limited, these findings are consistent with an international study (Rossow & Lauritzen, 1999
). The findings suggest that if a client presenting for treatment discloses a history of both self-destructive behaviours a thorough assessment should be conducted as an underlying comorbid problem could complicate clinical care. To decrease the risk of subsequent non-fatal overdose and suicide attempt events any identified comorbid problems should be dealt with concurrently in conjunction with opioid dependence. Additionally, the identification of a third dual diagnosis group of individuals highlights an important theoretical and conceptual issue for future studies to be aware of. The results suggest that if these groups are not assessed as mutually exclusive categories and the characteristics of this third dual diagnosis group are ignored the findings will be limited.
Non-fatal overdoses and suicide attempts seem to be distinct problems requiring different prevention strategies. For suicide attempts the clinical implications appear to focus on addressing and treating underlying psychological conditions, whereas for non-fatal opioid overdose harm minimisation strategies appear to be paramount to decreasing the associated risk. The findings suggest that individuals seeking treatment for psychological disorders should be primarily assessed for suicidal risk. Alternatively, the findings suggest that those who inject opioids are at an increased risk of overdose; consequently treatment could be focused on educating individuals on how to manage overdose situations, as well as focusing education campaigns on safer injecting practices. Sedative dependence was associated with non-fatal opioid overdose, and polydrug use has been found to be highly prevalent among opioid users (Darke, Ross, & Hall, 1995
). Considering this, a component of treatment could also be to educate opioid users on which combinations of drugs increase an individual’s risk of overdose. Additionally, treatment could focus on addressing and stabilising impulsivity levels, as well as teaching individuals to recognise high risk impulsive situations.
A number of limitations exist in the current study. It is unclear if our results are generalisable to other populations of opioid-dependent individuals who have never received methadone maintenance treatment. Our results are, however, comparable with a number of other studies (Ravndal & Vaglum, 1999
; Vingoe et al., 1999
). It is also possible that we may have failed to measure the contribution of other non-assessed correlates. Additionally, it is not possible to generalise the findings of this study to fatal overdose and suicide cases.
The study relies on self-report data and an amount of recall bias is introduced when assessing lifetime prevalence. These measures are commonly used in studies on illicit drug users, however, and have been shown to be adequately valid and reliable (Darke, 1998
; Dougherty et al., 2004
). The study was also reliant on the respondents’ determination of suicidal vs. non-suicidal behaviour. This limitation was minimised, however, by the use of standard definitions and the inclusion of questions which assess suicidal intent. There is also the potential that under-reporting existed in this study if the overdose did not result in complete respiratory arrest and occurred among an opioid user who was injecting alone.
Despite these limitations, this study has improved on previous work conducted by comparing multiple known correlates for non-fatal overdose and suicide attempts using mutually exclusive categories. This type of analysis was particularly important considering the substantial overlap which was found to exist between the groups.