Drug Dependence, psychological and sometimes physical state characterized by a compulsion to take a drug in order to experience its psychological effects. Psychological dependence, or habituation, is present when the compulsion to take a drug is strong, even in the absence of physical withdrawal symptoms. The drugs that are commonly abused, besides substances such as alcohol and tobacco, can be grouped into six classes: the opioids, sedative-hypnotics, stimulants, hallucinogens, cannabis, and inhalants. Opioids
The class of opioids includes drugs derived from oopium (such as morphine and heroin) and its synthetic substitutes (such as methadone). Medically, morphine is a potent pain reliever; indeed, it is the standard by which other pain-relieving drugs are measured. It and other opium derivatives also suppress coughing, reduce movements of the intestine (providing relief from diarrhoea), and induce a state of psychological indifference. Heroin, a preparation synthesized from morphine, was introduced in 1898 as a cough suppressant and nonaddicting substitute for morphine. The addictive potential of heroin wwas soon recognized, however, and its use was prohibited in many countries, even in medical practice. Users report that heroin produces a „rush“ or a „high“ immediately after it is taken. It also produces a state of profound indifference and mmay increase energy. Opioids produce different effects under different circumstances. The drug taker_s past experience and expectations have some influence, as does the method of administering the drug (by injection, ingestion, or inhalation). Symptoms of withdrawal include kicking movements in the legs, anxiety, insomnia, nausea, sweating, cramps, vomiting, diarrhoea, and fever. During the 1970s, when scientists isolated substances called enkephalins, naturally occurring opiates in the brain, they discovered what many believe to be the reason behind physical dependence on opioids-that is, the drugs are thought to mimic the action of enkephalins. If true, this hypothesis suggests that physical dependence on the opioids may develop in those who have a deficiency of these natural substances. Stimulants
Commonly abused stimulants are cocaine and ddrugs of the amphetamine family. Cocaine, a white, crystalline powder with a bitter taste, is extracted from the leaves of the South American coca bush. It is used medically to produce anaesthesia for surgery of the nose and throat and to constrict blood vessels and reduce bleeding during surgery; but abuse, which increased considerably in the late 1970s, can lead to severe physiological and psychological problems. A highly addictive, smokable form of cocaine, „crack“, appeared in the 1980s. Amphetamines, introduced iin the 1930s for the treatment of colds and hay fever, were later found to affect the nervous system. For a while they were commonly used as an appetite suppressant by people trying to lose weight. Today their use is restricted primarily to the treatment of narcolepsy, a sleep disorder characterized by sudden sleep attacks throughout the day, and of hyperactivity in children, in whom amphetamines produce a calming effect. For adults, however, amphetamines rightfully earn their common name, „speed“. These drugs heighten alertness, elevate mood, and decrease fatigue and the need for sleep, but they often make users irritable and talkative. Both cocaine and amphetamines, after prolonged daily use, can produce a psychosis similar to acute schizophrenia. A designer drug, 3,4-methylene dioxymethamphetamine, also know as „Ecstasy“ or „E“, gives users a great sense of wellbeing; affection for all those around them; increased energy; and, sometimes, hallucinations. Associated with rave culture, its adverse effects can make users feel ill or experience a sense of loss of control, dehydration, and long-term memory and weight loss. There have been some deaths associated with taking Ecstasy and other drugs at raves. Tolerance to both the euphoric and appetite-suppressing effects of amphetamines and cocaine ddevelops rapidly. Withdrawal from amphetamines, particularly if the drug is injected intravenously, produces depression so unpleasant that the drug user has a powerful incentive to keep taking the drug until he or she collapses. Hallucinogens
Hallucinogens are not used medically in most countries except occasionally in the treatment of dying patients, people with mental illness, drug abusers, and alcoholics. Among the hallucinogens that were widely abused during the 1960s are lysergic acid diethylamide, or LSD, and mescaline, which is derived from the peyote cactus. Although tolerance to these drugs develops rapidly, no withdrawal syndrome is apparent when they are discontinued. Phencyclidine, or PCP, known popularly by such names as „angel dust“ and „rocket ...