Resumo de Drug Addiction

Drug addiction, substance dependence or chemical dependency is the compulsive use of psychoactive drugs, to the point where the user has no effective choice but to continue use. The phenomenon of Drug addiction has occurred to some degree throughout recorded history, though modern agricultural practices, improvements in access to drugs, and advancements in biochemistry have exacerbated the problem significantly in the 20th century with the introduction of purified forms of active biological agents, and with the synthesis of hitherto unknown substances, such as methamphetamine.The alleged addictive nature of drugs varies from substance to substance, and from individual to individual. Drugs such as codeine or alcohol, for instance, typically require many more exposures to addict their users than drugs such as heroin or cocaine. Likewise, a person who is psychologically or genetically predisposed to addiction is much more likely to suffer from it.Although dependency on hallucinogens like LSD otherwise known as "acid" and psilocybin is listed as Substance-Related Disorder in the DSM-IV, most psychologists do not classify them as addictive drugs. Experts on addiction say that the use of LSD and psilocybin causes neither psychological nor physical dependency. Many users report feeling less desire to use these drugs after every use.There is anecdotal evidence which emerges of psychological addiction to recreational stimulants such as MDMA (Ecstasy) and a dissociative psychedelic Ketamine. Pills sold on the street as "ecstacy" often contain adulterants, which may be a contributing factor.Drug addiction has two components: physical dependency, and psychological dependency. Physical dependency occurs when a drug has been used habitually and the body has become accustomed to its effects. The person must then continue to use the drug in order to feel normal, or its absence will trigger the symptoms of withdrawal. Psychological dependency occurs when a drug has been used habitually and the mind has become emotionally reliant on its effects, either to elicit pleasure or relieve pain, and does not feel capable of functioning without it. Its absence produces intense cravings, which are often brought on or magnified by stress. A dependent person may have either aspects of dependency, but often has both."Chipping" is also a term used to describe a pattern of drug use in which the user is not physically dependent and sustains 'controlled use' of a drug. This is done by avoiding influences that reinforce dependence, such that the drug is used for relaxation and not for escape.
The basis for addiction
Scientists have long accepted that there is a biological basis for drug addiction, though the exact mechanisms responsible are only now being identified. It is believed that addictive substances create dependence in the user by changing the brain's reward functions, located in the mesolimbic dopamine system?the part of the brain that reinforces certain behaviors such as eating, sexual intercourse, exercise, and social interaction. Addictive substances, through various means and to different degrees, cause the synapses of this system to flood with excessive amounts of dopamine, creating a brief rush of euphoria more commonly called a "high".Although the high may last only a few minutes, it also produces more longer-lasting effects in the brain. Dopamine signals occurring normally in the reward system (traveling from the ventral tegmental area to the nucleus accumbens) lead to the activation of proteins designed to calm the initial reaction and foster a continued desire to pursue the behavior responsible. Addictive substances create a greater than normal dopamine release, and the subsequent reactions of the brain are greatly exaggerated as well. The amygdala, hippocampus, and frontal cortex associate the use of the drug with intense pleasure and well-being; an association that is strengthened with each exposure, and which over tcomes to dominate normal thoughts and desires. When cravings for the drug are no longer controllable, the user is considered addicted. There seems to be a genetic component to addiction. Pankaj Sah of Australian National University believes that chronic marijuana users are self medicating for anxiety problems.In addition Dr. Lonny Shavelson, in his book "Hooked," has reported that 70% of female heroin addicts were sexually abused as children.

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