Distinguishing Between Physiological Dependence and Substance Use Disorder: Response to Ruan et al.

To the Editor: We thank Dr. Ruan and colleagues for their interest in our article (1). They raise two important issues. First, they point out that the terminology used to refer to substance use disorders is inconsistent, particularly when referring to opioids. We agree. We have previously addressed differences between nonmedical opioid use and opioid use disorder, including trends (2), correlates (3), and relationships between them (4).

We also agree that clinicians, researchers, and policy makers often mistakenly conflate the concepts of physiological dependence, which includes tolerance and withdrawal, and substance use disorder. We are pleased to see this key distinction being taken seriously by medical specialties beyond psychiatry. We hope that this will contribute to improved assessment and treatment of patients with pain, reduced risk of nonmedical opioid use, and a lower incidence of opioid use disorder. To minimize confusion, we chose in our article to use DSM-IV criteria, which was the official classification system when the data were collected.

The second issue raised by Dr. Ruan and colleagues is whether use of DSM-IV, rather than DSM-5, compromises our results. Clinical and epidemiological samples have demonstrated a high degree of concordance between DSM-IV and DSM-5 opioid use disorder diagnoses (5, 6). The robustness of our analyses to analytic method suggests that the results are unlikely to be sensitive to these changes in nomenclature. We are not aware of nationally representative samples that have been longitudinally evaluated to assess the relationship between pain and prescription opioid use disorder using DSM-5 criteria. We agree with Dr. Ruan and colleagues that, given the importance of this topic, such a study would be an important contribution.