To understand fully you must be aware of the difference between tolerance, physical dependence, and addiction:
As a person takes opioids for an extended period of time, they become less sensitive to it and require more to achieve the same effect. Receptors in the brain become less sensitive. This means they need more and more opioid to achieve the same effect. This is called tolerance. When the body can no longer make enough natural opioids to satisfy the less sensitive receptors, the body becomes dependent on the external source. This is physical dependence.
"Physical Dependence" is a physiological state of adaptation to a substance, the absence of which produces symptoms and signs of withdrawal. It is possible to be physically dependent on a drug without being addicted to it. Physical dependence is the result of physical changes in the brain. It is not a matter of willpower rather it is actual physiology.
Addiction is defined as a behavioral syndrome characterized by the repeated, compulsive seeking (psychological dependence) or use of a substance despite adverse social, psychological, and/or physical consequences, along with the physical need for an increased amount of a substance as time goes on to achieve the same desired effect. Addiction is often (but not always, as with an addiction to gambling) accompanied by tolerance, physical dependence, and withdrawal syndrome.
People are dependent on water and food but are not addicted to them. If a cancer patient is taking large doses of painkillers, he/she will become tolerant and physically dependent on them (meaning they will experience withdrawal symptoms if the drug is abruptly removed) but they are not necessarily addicted to it (meaning they will not seek out the drug despite adverse consequences once the drug is no longer needed for pain).
Addiction is a disorder that requires treatment while physical dependence is not. This is important to understand in order to be able to discern between switching one addiction for another and treatment.
The American Academy of Pain Medicine, American Pain Society, and American Society of Addiction Medicine, recognizes these definitions below as the current accepted definitions.
Addiction is a primary, chronic, neurobiologic 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.
II. Physical Dependence:
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.
Addiction is uncontrollable compulsive behavior caused by alterations of parts of the brain from repeated exposure to high euphoric responses.
The Essence of Drug Addiction- By Alan I. Leshner, Ph.D., Former Director, National Institute of Drug Abuse, National Institutes of Health
What’s in a Word? Addiction Versus Dependence in DSM-V - CHARLES P. O’BRIEN, M.D., PH.D. NORA VOLKOW, M.D.
NIDA publication: The Neurobiology of Opioid Dependence: Implications for Treatment Thomas Kosten MD, Tony George MD
The American Academy of Pain Medicine, American Pain Society, American Society of Addiction Medicine - consensus document – February 2001,
American Academy of Pain Medicine - http://www.painmed.org/
American Pain Society - http://www.ampainsoc.org/
American Society of Addiction Medicine - http://www.asam.org/
To suppress the debilitating symptoms of cravings and withdrawal, enabling the patient to engage in therapy, counseling and support, so they can implement positive long-term changes in their lives which develops into the new healthy patterns of behavior necessary to achieve sustained addiction remission. - explain -