Etiology of Chronic Pain and Mental Illness: How To Assess Both
Last month in the first part of this three-part series, we explored the biopsychosocial components of chronic pain.1 As psychosocial components have been explored, it has become clear that chronic pain is associated with high rates of mental health disorders. The comorbid relationship between chronic pain and these disorders has been identified in patients with chronic low back pain (LBP), chronic work-related musculoskeletal pain disability, chronic arthritis, headache/migraine, temporomandibular joint disorder (TMD), upper extremity disorders such as carpal tunnel syndrome, fibromyalgia, and a heterogeneous chronic pain group.2-14 Although the prevalence rates differ depending on clinical conditions and clinical contexts, most study patients demonstrated a higher prevalence of depression, anxiety disorders, and substance use disorders compared with those with acute chronic pain or the general population (Table, see page 83).
Among the studies using standard measures for diagnostic assessment (eg, the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders [DSM] [SCID]),15 major depression was commonly present. For example, rates of current major depressive disorder (MDD) ranged from 23% to 78% in chronic pain groups compared with rates of 5% to 17.1% in the general population.16-18 Many patients with chronic pain also appeared to suffer from symptoms of anxiety. Several studies have reported that 10.6% to 62.5% of patients with chronic pain meet current criteria for any anxiety disorder compared with 1% to 25% in the general population.16-18 Current substance use/abuse was frequently found. The percentage of patients with chronic pain meeting current criteria for substance disorders (4.3%-40%) was higher than general population ranges (15%-26.6%).16-18 Although some patient groups reported greater prevalence rates of certain Axis I disorders, the overall prevalence rates in patients with chronic pain were much greater than those in the general population.
In addition, patients with chronic pain were diagnosed with many more Axis II personality disorders than individuals in the general population. Axis II personality disorders have been examined in several studies of DSM diagnoses in individuals with chronic pain, and it has been found that 21% to 70% of patients received some personality disorder diagnosis.3,4,11,14,15 More specifically, personality disorders were very common, with paranoid (9%-33%), borderline (10%-27.5%), and obsessive-compulsive (10%-16.3%) personality disorders, as well as passive-aggressive personality traits (14%-14.9%) being diagnosed in chronic pain patient groups.
Theses prevalence rates suggest a significant association between a chronic pain population and several types of psychopathologic disorders, MDD, anxiety, substance use, and personality disorders. Therefore, it is essential to use a comprehensive assessment battery in order to evaluate the comorbid relationship between chronic pain and psychiatric disorders and then design the most effective treatment plan. This article reviews a number of assessment tests that are commonly available. The third part of the series, which will be published next month, will review treatment of the comorbid patient.
Accurately assessing psychopathology in patients with chronic pain is a fundamental component crucial to treatment and the evaluation of outcomes. Unfortunately, there are many barriers present in accurately diagnosing and assessing severity of psychosocial distress. Various methods of assessment used include self-report questionnaires, clinical interviews, and structured interviews. Although no self-report measure can take the place of a trained clinician’s diagnosis, logistical limitations exist, and not every patient can receive a full psychosocial evaluation from a trained clinical psychologist or psychiatrist specializing in chronic pain management. These limitations have been the impetus for the development of a battery of screening instruments that have proven to be quite successful in their ability to diagnose and predict outcomes.19
An increasing number of nonpsychiatric physicians are administering various psychosocial questionnaires during the evaluation process that aid in identifying which patients may need further psychosocial assessment.20 There is even evidence suggesting that the use of psychometric assessment is better than either magnetic resonance imaging (MRI) or diskography in predicting future back pain disability.21,22 The following section lists and briefly explains some of the psychosocial measures and mental health instruments typically used in a full-spectrum assessment of patients with chronic pain.
Million Visual Analog Scale
The Million Visual Analog Scale (MVAS) is a self-report instrument measuring pain perception and subjective disability. It was originally developed by Million and colleagues, with modifications to cutoffs developed by Anagnostis et al.23,24 The MVAS is a 15-question assessment in which each response is rated as a point on a line marked in increments from 0 to 10. The sum of the 15 responses determines the final score on this assessment such that 0 is no disability; 1 to 40 is mild disability; 41 to 70 is moderate disability; 71 to 100 is severe disability; 101 to 130 is very severe disability; and 131 to 150 is extreme disability. The MVAS is particularly useful in instances when patients’ self-report of pain exceeds that which would be projected given physical findings; the psychosocial components are considered in the patients’ disability.25 This measure was originally designed to assess physical functioning and disability related primarily to patients with chronic LBP. The MVAS is effective as a simple disability rating scale and is useful in predicting treatment outcomes for patients with chronic disabling spinal disorders.24
Pain Disability Questionnaire
The Pain Disability Questionnaire (PDQ) is used to measure perceived pain and disability.26 The PDQ is a 15-item questionnaire developed from a collaboration of experienced healthcare professionals and a number of drafts that incorporated various dimensions of other instruments, such as the 36-item Short Form Health Survey [SF-36], MVAS, West Haven–Yale Multidimensional Pain Inventory [MPI], and the Roland-Morris Disability Questionnaire, used in assessing disability status related to pain. Each question presents an analog scale on which patients respond by indicating, on a 10-cm line, their level of pain associated with each domain. The PDQ contains two factors, a functional status component and a psychosocial component. The individual items attributed to each factor are added to generate the score for the two different components, and the total score is composed of all the responses added together. This measure has demonstrated solid psychometric properties, including validity, reliability, and responsiveness to change.26