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A relapse or recidivism is a recurrence of a past (typically medical) condition. For example, MS or malaria often exhibit peaks of activity and sometimes long periods of dormancy. Relapse, in relation to drug abuse, is resuming the use of a drug or a chemical substance after one or more periods of abstinence. The term is a landmark feature of both substance dependence and substance abuse, which are learned behaviors, and is maintained by neuronal adaptations that mediate learning and processing of various motivational stimuli.〔 An important aspect of drug use is the propensity for repeated use and dependence, tendencies that are influenced by the nature of the drug itself and thus vary from substance to substance. Those substances that are cleared from the body most quickly, those with the highest pharmacological efficacy, and those that induce the highest tolerance elicit the most severe tendency for relapse in users. Drug dependence can lead to increased tolerance to the substance in question, cravings, and withdrawal if the drug use ceases. ==Causes== Substances that may cause dependence or abuse can be classified based upon whether or not they produce a withdrawal syndrome when drug use stops. * Stimulants increase activity in the cerebral cortex leading to increased motor activity. * *Cocaine * *Amphetamines * *Methamphetamines * Depressants slow down neuronal activity. * *Benzodiazepines (i.e.: Xanax) * *Opioids activate or block opioid receptors in the brain typically to reduce the effect of pain. Some common opioids are: * * *Morphine * * *Methadone * * *Opium * * *Heroin * *Alcohol produces disinhibition in the nervous system when introduced, and it depresses the frontal cortex while speeding up the rest of the brain. This can lead to decreased ability to perceive and evaluate risks and make good decisions, and other characteristics of what is commonly known as intoxication. * Nicotine is neither a stimulant nor a depressant but rather a chemical that is absorbed by the skin and mucous membranes and activates the nicotinic acetylcholine receptors. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「relapse」の詳細全文を読む スポンサード リンク
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