"Although MMTP [Methadone Maintenance Treatment Program] patients were significantly more likely than inpatients to report chronic pain, and almost a quarter reported that pain was one of the reasons for first using drugs, there was relatively little evidence that pain was associated with current levels of substance abuse. In the multivariate analysis, the associations between chronic pain and the substance abuse behaviors observed in the bivariate analysis (pain as a reason for first using drugs and drug craving) were not sustained. Moreover, the bivariate associations that were found in the inpatient group between chronic pain and multiple drug use, and between pain and the use of illicit drugs to treat pain complaints, were not identified among MMTP patients."
Rosenblum A, Joseph H, Fong C, Kipnis S, Cleland C, Portenoy RK. Prevalence and Characteristics of Chronic Pain Among Chemically Dependent Patients in Methadone Maintenance and Residential Treatment Facilities. JAMA. 2003;289(18):2370–2378. doi:10.1001/jama.289.18.2370