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Chronic pain is frequently described as an intractable pain that does not serve an adaptive purpose (ie, alerting the organism to danger and/or injury), often lasting longer than 6 months with no identifiable medical explanation, commonly localized to the lower back, knee joints, head, and neck.1-3
Traditionally, chronic pain was characterized by the length of time the pain persisted. More recent conceptualizations have, however, introduced other concessions. For example, the International Association for the Study of Pain defines chronic pain as being “without biological value … persist[ing] beyond the normal tissue healing time … as determined by common medical experience [and/or] a persistent pain that is not amenable, as a rule, to treatments based upon specific remedies.”1
Notwithstanding the foregoing updates in the definition of chronic pain, the manifestation and experience of pain is variable and still does not capture the varieties of chronic pain, wherein some forms may display remission and recurrence (eg, migraine headaches) whereas others are more likely to be progressive (eg, rheumatoid arthritis).
The subjective experience of pain is often associated with debilitating consequences including psychological stress, social isolation, and cognitive impairment.4 The prolonged experience of chronic pain and its psychological consequences may act as a prodrome to mental illness, notably major depressive disorder (MDD).
The determinants of chronic pain largely resemble those associated with MDD (eg, age, gender and socio economic status).1 The latter observation is further supported by reports from the World Health Organization indicating that the 12-month prevalence of chronic pain is approximately 37% in developed nations, as compared to 41% in developing nations.1,5
The number of undetected cases of MDD among individuals presenting with chronic pain as the primary concern is becoming increasingly recognized as a barrier to the appropriate identification, diagnosis, and treatment of this highly prevalent mood disorder.4 This is particularly worrisome since comorbid pain and depressive symptomatology are associated with a higher rate of antidepressant switching, which is reported to have a negative impact on likelihood of recovery with each subsequent failed treatment. 6-9
To examine available evidence and to address these concerns, in a recent review, researchers aimed to identify whether any screening tools are currently available to evaluate both pain and depression. They also sought to delineate available methods of identifying comorbid depression and pain in a primary care setting.
They found that many were using a general screening tool that is capable of effectively assessing both depressive symptomatology and chronic pain. However, a validated screening metric that evaluates both symptoms of depression and pain does not currently exist. Because physicians commonly encounter patients with comorbid chronic pain and mood disorders, a validated screening tool is needed.
The authors also evaluated currently available screening tools for depression or chronic pain. They noted that, although a number of screening tools for pain are currently available, the majority are specifically validated to identify certain types of pain (eg, neuropathic, back pain, knee pain).4
Taken together, the authors suggested that the most relevant screening tool that could be repurposed to explore the presence of depressive symptoms in individuals with chronic pain was via the National Institute for Health and Care Excellence (NICE) guidelines for identifying chronic physical health problems in primary care. These guidelines recommend that all patients are asked 2 standard questions about depression, prompting further questioning if either elicits a positive response.
Similar to MDD, anxiety is also highly comorbid with chronic pain, and vice versa. For example, data on lifetime prevalence of panic disorder, agoraphobia, social anxiety disorder, generalized anxiety disorder, or post-traumatic stress disorder (PTSD) indicate a 2 to 3-fold increase in individuals who experience chronic pain, especially when the pain is localized to the lower back or neck.10
It is hypothesized that the relationship between anxiety and chronic pain is, at least partially, subserved by physiological arousal (eg, increased muscular tension and blood flow, elevated blood pressure and heart rate), wherein prolonged arousal and the activation of inter-related neural, endocrine, and immunological processes (eg, cytokine and hormone release) contributes to detrimental effects on muscle, bone, and neural tissue over time, due to a chronic activation of the stress response.
Despite the significant advances in understanding of the pathophysiology of persistent pain, the management and treatment of chronic pain – especially among individuals with mental illness – has not significantly improved.
In an increasingly aging population, the prevalence of chronic pain will continue to increase and will result in additional health service costs.4,11 The development of screening tools and researching of potential mechanisms for moderating/mediating chronic pain should thus be considered a priority.
References
1. Katz J, Rosenbloom BN, Fashler S. Chronic pain, psychopathology, and DSM-5 somatic symptom disorder. Can J Psychiatry 2015;60(4):160-167.
2. Schopflocher D, Taenzer P, Jovey R. The prevalence of chronic pain in Canada. Pain Res Manag 2011;16(6):445-450.
3. Johannes CB, Le TK, Zhou X, Johnston JA, Dworkin RH. The prevalence of chronic pain in United States adults: results of an Internet-based survey. J Pain 2010;11(11):1230-1239.
4. Cocksedge Karen SRSC. Depression and pain: the need for a new screening tool. Progress in Neurology and Psychiatry 2016;26-31.
5. Tsang A, Von KM, Lee S et al. Common chronic pain conditions in developed and developing countries: gender and age differences and comorbidity with depression-anxiety disorders. J Pain 2008;9(10):883-891.
6. McIntyre RS, Filteau MJ, Martin L et al. Treatment-resistant depression: definitions, review of the evidence, and algorithmic approach. J Affect Disord 2014;156:1-7.
7. Kennedy SH, Lam RW, Parikh SV, Patten SB, Ravindran AV. Canadian Network for Mood and Anxiety Treatments (CANMAT) clinical guidelines for the management of major depressive disorder in adults. Introduction. J Affect Disord 2009;117 Suppl 1:S1-S2.
8. McIntyre RS, O’Donovan C. The human cost of not achieving full remission in depression. Can J Psychiatry2004;49(3 Suppl 1):10S-16S.
9. McClintock SM, Husain MM, Wisniewski SR et al. Residual symptoms in depressed outpatients who respond by 50% but do not remit to antidepressant medication. J Clin Psychopharmacol 2011;31(2):180-186.
10. Asmundson GJ, Katz J. Understanding the co-occurrence of anxiety disorders and chronic pain: state-of-the-art.Depress Anxiety 2009;26(10):888-901.
11. Lynch ME. What Is the Latest in Pain Mechanisms and Management? Can J Psychiatry 2015;60(4):157-159.
This article originally appeared on Clinical Pain Advisor
