Assessing the prevalence of opioid misuse, abuse, and addiction in chronic pain

Ballantyne, Jane C.

Pain:

April 2015 - Volume 156 - Issue 4 - p 567–568

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Department of Anesthesiology and Pain Medicine, University of Washington School of Medicine, Seattle, WA, USA

Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.

Received January 13, 2015

Accepted January 16, 2015

In their systematic review, Vowles et al.¹⁶ tackle the debatably impossible task of estimating the prevalence of opioid misuse, abuse, and addiction in chronic pain. They make their assessments utilizing rate estimates from the literature (this literature happens to be mostly a United States literature). Why impossible—because it is hard to understand what addiction actually is when it arises during pain treatment with opioids. Rather sensibly, the authors use broad categories where “misuse” is using opioid not as prescribed, “abuse” is intentional use for nonmedical purpose, and “addiction” is compulsive use (see article for more complete descriptions). These definitions are based on recent consensus statements from expert panels and additional expert opinion.^4,12,14–16 The authors do not get bogged down in language used in Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition and International Classification of Diseaseswhere “abuse” and “dependence” carried different meanings to those generally understood and confused people's understanding of addiction, as well confounding efforts to quantify addiction prevalence.¹ Perhaps not surprisingly, given the difficulty we have with agreeing on definitions or understanding what addiction is when it arises during the treatment of pain with opioids, rates of problematic use extracted from studies are broad ranging (from <1% to 81%). Abuse is reported in only one study, while average rates of misuse range from 21% to 29% and average rates of addiction range from 8% to 12%. This is useful information in terms of understanding the scale of misuse and addiction. But, could rates of addiction have been underestimated because there cannot be clear distinctions between misuse and addiction, despite the apparent clarity of the definitions?

The neural processes of opioid addiction have been learned from animal and human studies in subjects that are receiving opioids not as pain treatment, but for other purposes.

 In the case of human studies, subjects have generally been using opioids for recreational purposes.¹¹ What is known from such studies is that adaptations in the reward center in the brain (the mesocorticolimbic system) and in central noradrenergic nuclei result in the state of dependence whereby unpleasant psychological and physical symptoms result in a need to obtain opioid should levels decline or needs increase.^6,8,11Dependence is known to be a powerful driver of opioid-seeking behavior. In fact, established opioid addicts seek opioids not to provide euphoria but to avoid dysphoria and other unpleasant symptoms.⁸ What turns opioid seeking for the relief of withdrawal into the state of compulsive opioid seeking that defines addiction is not fully understood, but irreversibility is a feature, and is believed to be due to the secondary process of memory formation (memory, ie, of obtaining or procuring drug) in structures such as the amygdala, hippocampus, and cerebral cortex.^5,13 In the case of recreational or illicit use of opioids, dependence without addiction does not arise because the progression in this case is fairly clear from occasional use involving procurement but without dependence, through repeated procurement, to addiction with dependence. Because in the case of recreational or illicit use, the user must obtain or procure the drug, the clinical picture and the underlying drivers of addiction are relatively straightforward and well established.⁹

Not so in the case of opioid treatment of chronic pain. While there are similarities in that dependence will develop with continued use and will similarly be a powerful driver of opioid seeking (in fact dependence will be responsible for the state aptly described by patients themselves whereby they believe that they need opioids even when they have stopped providing good pain relief: “you see, they work, when I stop them, I get worse”).¹⁰ But in the case of chronic pain treatment, there are many other drivers of opioid seeking. Not least, of course, is seeking pain relief, but patients with pain could also be looking for relief of anxiety, depression, stress, or existential suffering. Patients having pain are typically prescribed opioids; therefore, they do not need to procure them. This has 2 implications: one that dependence may develop without addiction because there may be long-term use without aberrant behaviors; and second that the progression toward and the factors underlying addiction when it does occur are extremely complex.³ In fact, do we really know when the dependence that arises in opioid-treated pain patients becomes addiction? Does the absence of the defining characteristics of impaired control over drug use, compulsive use, continued use despite harm and craving mean as much in a person essentially maintained on opioids, as it does in a person needing to procure drug? And where in the large gray zone between clearly addicted and clearly not addicted, can a line be drawn that not only clearly defines addiction but would also define who is suitable for addiction treatment, or at least addiction-type treatment?²Rather than trying to identify such a line or to distinguish between misuse, abuse, and addiction, it may be better to accept that the state of dependence (which could variously be manifest as misuse, abuse, or addiction), or what has been termed “complex persistent dependence” (a state of dependence that, like addiction, does not easily reverse), is akin to addiction and worthy of addiction-type treatment.³

Vowles et al.¹⁶ end their article with the comment that it is not certain whether the unclear benefits derived from opioids compensate for the additional burden of the “unintended” consequences to patients and health care systems. Adaptations to continuous opioid use are responsible not only for dependence and all its consequences but also for diminished analgesic efficacy. If the result is much harm with little benefit, then we really do need to re-examine chronic opioid therapy in terms of who are suitable candidates and what are suitable precautions. The value of the Vowles et al.¹⁶ analysis is that it provides an estimate of the scope of misuse and addiction, although for the reasons already stated, it may actually underestimate addiction rates. All patients exhibiting misuse, abuse, or addiction, and the Vowles et al.¹⁶ analyses suggest there are many, are likely to improve in addiction-type programs such as program by Jamison et al, which provides a low-intensity intervention that includes mentoring and education.^7,16 Hopefully more judicious prescribing will reduce unintended consequences, but in the meantime, those already afflicted by dependence, whether or not this is addiction, need appropriate care. The implication of the Vowles et al.¹⁶ findings is that a very large contingent needing care already exists in the United States specifically, and steps need to be taken urgently in the United States to provide such care.