¶ … drug-Related terms such as tolerance, withdrawal, rebound, physical and psychological dependence. Tolerance

Tolerance is a form of physical dependence on a drug. It occurs when the body becomes accustomed to a drug and the nerve cells chemically and structurally counteract the drug's psychoactive effects. As a result, the drug abuser requires ever-increasing amounts of it to achieve the same physical and psychological effects. This condition is worsened when certain drugs are used at high doses for long periods (weeks or months), and may lead to more frequent use of the drug. Drug addicts often have to increase the dose to experience the same level of euphoria or "high" that they experience initially. ("Drug Dependence," Encarta)

Withdrawal

When drug addicts stop the use of a drug too quickly, they may suffer from physical discomfort which is known as "drug withdrawal." Drug withdrawal is frequently characterized by nausea, headaches, restlessness, sweating, and difficulty in sleeping. The severity of drug withdrawal symptoms varies depending on the drug involved, i.e., the withdrawal symptoms of 'hard' drugs such as heroin are more severe than for milder drugs such as

(Ibid.)
3. Rebound

'Rebound effect" is the reason why withdrawal symptoms occur. The physiological systems in our body are modified by the drug use; when the drug is suddenly withdrawn a rebound occurs in the modified physiological systems. For example, alcohol depresses the Central Nervous System; its withdrawal has the opposite effect, i.e., it stimulates the CNS. Amphetamine, on the other hand stimulates the CNS, so amphetamine withdrawal causes depression and a lack of energy. "Rebound," therefore, is the 'opposite effect' of the drug during its withdrawal. (Perkinson, para on Tolerance and Dependence)

4. Physical Dependence

Drug dependence, in general, is a compulsion to continue taking drugs in order to feel good or to avoid feeling bad.…