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Box 3.1

Definitions

Addiction. Substance dependence.

Craving refers to the intense desire for a drug and is the most difficult aspectof addiction to overcome.

Physiologcal dependence is diagnosed when there is evidence of either tolerance or withdrawal; it is sometimes, but not always, manifested in substance dependence.

Reinforcement. A drug-—or any other stimulus—is referred to as a reinforcer if exposure to it is followed by an increase in frequency of drug-seeking behavior. The taste of chocolate is a reinforcer for biting into a chocolate bar. Likewise, for many people the sensation experienced after drinking alcohol or smoking marijuana is a reinforcer.

Substance dependence is a cluster of cognitive, behavioral, and physiological symptoms indicating that a person continues use of the substance despite significant substance-related problems.

Tolerance is the most common response to repetitive use of a drug and can be defined as the reduction in responses to the drug after repeated administrations.

Withdrawal. The collective symptoms that occur when a drug is abruptly withdrawn are known as withdrawal syndrome and are often the only evidence of physical dependence.

dence, and withdrawal symptoms if the drug is stopped abruptly rather than gradually. For example, a hypertensive patient receiving a beta-adrenergic receptor blocker, such as propranolol, might have a good therapeutic response; but if the drug is stopped abruptly, there can be a withdrawal syndrome that consists of tachycardia and a rebound increase in blood pressure to a point that is temporarily higher than before administration of the medication began.

Because it is an illegal substance, some people consider any use of marijuana as substance abuse. However, this report uses the medical definition; that is, substance abuse is a maladaptive pattern of repeated substance use manifested by recurrent and significant adverse consequences.3 Substance abuse and dependence are both diagnoses of pathological substance use. Dependence is the more serious diagnosis and implies compulsive drug use that is difficult to stop despite significant substancerelated problems (see Box 3.2).



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