Prevalence of substance use and psychiatric disorders in a highly select chronic pain population.

Objective: To estimate the prevalence of self-reported substance use and psychiatric disorders in a highly select chronic nonmalignant pain population within a nonprimary care tertiary referral-only pain clinic.

Methods: A retrospective, cross-sectional study was accomplished via existing medical record review for 216 consecutive pain patients presenting to an independent neurodiagnostic clinic located in the southeastern United States, specializing in chronic, severe, and complex industrial injuries (e.g., multiple failed fusions, neuropathic pain), involving complex combinations of nocioceptive, neuropathic, and myofascial pain. De-identified self-report data from the Comprehensive Assessment and Psychological Evaluation (a structured diagnostic assessment interview compatible with DSM-IV-TR criteria, which assesses for symptoms of 8 Axis I and 6 Axis II disorders including substance-specific dependence and abuse) were obtained as part of the standard intake procedures for diagnostic determinations. Diagnostic assessment of substance use disorders was also independently verified by a physician certified by the American Society of Addiction Medicine.

Results: An extremely low prevalence of substance abuse and dependence diagnoses were found for 1.9% of the population, of which nearly 30% were not currently prescribed opioid medications for pain. One case of alcohol dependence and 3 cases of alcohol abuse were found. Psychiatric diagnoses, excluding substance use disorders, predominated as follows: major depressive disorder, 44.4%; posttraumatic stress disorder, 29.2%; and obsessive-compulsive personality disorder, 62.5%.

Conclusions: Certain populations of patients with complex nocioceptive, neuropathic, and myofascial pain syndromes may have a lower prevalence of substance use disorders than the general population. They also may have concurrent psychiatric disorders, which should be evaluated and treated concomitantly as part of their chronic pain treatment. Rates reported for possible obsessive-compulsive personality disorder may be reflective of patients' expected preoccupation with pain complaints. The low prevalence of substance use disorders may be attributable to the severity of their illness, the patients' inability to achieve pain relief and obtain pain medications easily, as well as their persistence in pursuing accurate diagnoses and treatment. Roughly one-third were not currently prescribed opioids at the time of the study, perhaps undercutting risk for opioid use disorder rates. Additionally, due to the tertiary referral nature of this clinic, patients with behaviors believed to be a manifestation of opioid use disorder may have already been selected out prior to referral to this clinic. A major limitation of this study was that it relied on a self-report assessment instrument and there were no drug screen findings to report. Such unique clinic characteristics and study limitations may narrow generalizability of results. Despite the low prevalence of substance use disorders observed for this clinic population, these patients must be continuously monitored for abuse, misuse, and diversion of their medication.