Research reportFactors associated with the development of depression in chronic non-cancer pain patients following the onset of opioid treatment for pain
Introduction
The global prevalence of chronic non-cancer pain (CNCP) is estimated at one adult in five, (Vos et al., 2012) with the 2010 Global Burden of Disease Study reporting chronic low back pain as the largest cause of years lost to disability (Hoy et al., 2014).
Pharmaceutical opioids are increasingly used for treatment of CNCP (Leong et al., 2009). Despite the link between CNCP and poorer mental health being well established in the literature (Fishbain et al., 1997, Kroenke et al., 2011), little is known about the impact that commencement of prescribed opioids may have on this relationship (i.e., is use of opioids associated with an increased or decreased likelihood of depression).
A growing body of research has focused on 'adverse selection' (Howe and Sullivan, 2014) whereby individuals with pre-existing mental illness are more likely to be prescribed pharmaceutical opioids for CNCP and at higher doses (Braden et al., 2009). A recent cohort study found individuals who were receiving opioid treatment were more likely to report high levels of psychological distress compared with individuals not receiving opioid medications (Rogers et al., 2013). Additionally, opioid-naïve patients with chronic pain without a recent history of depression have been found to be at greater risk of developing depression the longer they were taking opioid medications (Scherrer et al., 2014).
With an ageing population in Western countries and increasing opioid prescribing in many of these, it is timely to assess the possible association between pharmaceutical opioids and risk of developing depression. The current study examines data from a large community sample, including in-depth measures of mental health, and self-reported opioid consumption (rather than prescribing data), while controlling for severity of pain and pre-existing depression.
The aims of the study were as follows:
- (1)
to estimate the prevalence of depression that occurs after the onset of pain and also after the initiation of prescribed opioid treatment for pain;
- (2)
to determine demographic and clinical characteristics and factors associated with those who develop depression post-pain; and
- (3)
to determine demographic and clinical characteristics and factors associated with those who develop depression post-opioid treatment.
Section snippets
Study design
This study draws on baseline data collected for the Pain and Opioids IN Treatment (POINT) study, a national cohort of 1514 individuals taking pharmaceutical opioids for chronic non-cancer pain. Recruitment of this cohort has been described elsewhere (Campbell et al., 2014). In brief, community pharmacists referred patients prescribed strong opioids to complete a telephone interview and self-complete survey at baseline and then three further time points.
The study was approved by the Human
Demographic, pain and medication characteristics
Of the 1418 participants in this analysis, 44% were male with a median age of 58 years (IQR=48–68). The average pain duration was 10 years (IQR=4.5–20) with current pain severity rated at a mean of 5.1 (SD=1.8), and mean pain interference of 5.7 (SD=2.3) Participants reported taking pharmaceutical opioids continuously for a median of 4 years (IQR=1.5–10) with the average daily oral morphine equivalent dose being 70 mg (IQR=35–142 mg). Sixty-one per cent of participants reported a lifetime
Discussion
Although the association between chronic pain and depression has been documented (Fishbain et al., 1997, Kroenke et al., 2011), less work has examined the potential impact of pharmaceutical opioid therapy on the timing of development of depression. The current study aimed to identify factors associated with depression developing after the commencement of opioid medications that might differ from those associated with the onset of pain itself. Where previous research has been limited by
Conclusions
Although there are similarities between those who develop depression following the onset of pain and those who develop depression after initiating opioid treatment for pain, the latter group, especially those commencing opioids at a younger age appear to be a greater risk of poorer outcome of treatment for pain and of developing difficulties with their opioid medications. These results reflect the complex comorbidities of chronic pain, especially depression and underscore the necessity for
Role of funding source
This study received funding from the Australian National Health and Medical Research Council (NHMRC, #1022522). RPM, SN, BL and LD are supported by NHMRC research fellowships (#1041472, #1073858, #1013803, #569738 and #1045318). The National Drug and Alcohol Research Centre at the University of NSW is supported by funding from the Australian Government under the Substance Misuse Prevention and Service Improvements Grant Fund. The funder had no role in the design, conduct, analysis,
Conflict of interest
RPM, RB, SN, GC, BL, and LD have all been investigators on untied investigator-driven educational grants funded by Reckitt Benckiser for post-marketing surveillance studies of buprenorphine-naloxone tablets and film, development of an opioid-related behaviour scale, and/or a study examining the uptake of opioid substitution therapy among chronic non-cancer pain patients. RB, BL and LD have received an untied educational grant from Mundipharma for post-marketing surveillance studies of
Acknowledgements
The authors would like to acknowledge and thank the POINT participants for giving their time and sharing their experiences.
Thanks to Chief Investigators Wayne Hall, Nicholas Lintzeris and Fiona Shand who assisted with development of the overall study design. Thanks to Jessica Belcher, Sarah Freckleton, Bianca Hoban, Anika Martin, Ranira Moodley, and Rachel Urquhart-Secord at NDARC, for their contribution to data collection.
Thanks to the Pharmacy Guild of Australia, the NSW Pharmacy Guild, and
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