Addiction is a primary, chronic, neurobiological disease, with genetic, psychosocial and environmental factors influencing its development and manifestations. It is characterized by behaviors that include one or more of the following: impaired control over drug use, compulsive use, continued use despite harm, and craving.

Physical dependence is a state of adaptation that is manifested by a drug-class-specific withdrawal syndrome that can be produced by abrupt cessation, rapid dose reduction, decreasing blood level of the drug, and/or administration of an antagonist.

Tolerance is a state of adaptation in which exposure to a drug induces changes that result in a diminution of one or more of the drug’s effects over time. An increasing need may also result from progression of disease.

Pseudo-addiction is a term that has been used to describe patient behaviors that may occur when pain is undertreated. Patients with unrelieved pain may become focused on obtaining medications, may “clock watch,” and may otherwise seem inappropriately drug seeking. The term should not be construed as justifying non-adherence behaviors and should never be used in lieu of an appropriate diagnosis of addiction or illicit use. Nonetheless, it is an important reminder that unrelieved pain can drive aberrant drug-related behaviors, whether or not the comorbidity of addiction exists. Theoretically, aberrant behavior driven by poorly controlled pain can be distinguished from abuse determined by other factors by the improvement that occurs when the pain is effectively treated. The decision to use an opioid or other controlled drug in an effort to reduce pain in this context is enormously challenging, however, and often requires the input of specialists.

A structured evidence-based review of studies examining the development of abuse/addiction and aberrant drug-related behaviors in patients with chronic nonmalignant pain who were exposed to chronic opioid therapy found that a small percentage of patients (3.27%) developed abuse/addiction. Patients without a current or past history of alcohol or illicit drug use or abuse/addiction were less likely to develop aberrant behavior. Another recent systematic review assessing the prevalence of opioid dependence syndrome in adults (most of whom lacked a history of substance abuse) found a median value of 4.5%. However, urine toxicology studies have revealed that a substantially higher number of patients (21% to 45%) maintained on chronic opioid therapy have positive urine screens, defined as the presence of an illicit drug or an additional non-prescribed controlled drug in the urine, or the absence of the prescribed opioid.