Any chemical substance that alters normal biological processes.
Psychoactive drugs alter behavior, thought, or emotions by changing biochemical reactions in the nervous system. They can be addictive (habit-forming), and they can be legal or illegal.
Drug abuse is the self-administration of drugs in ways that depart from medical or social norms, and it can lead to psychological or physical dependence. Physical dependence, or addiction, which can occur together with psychological dependence, is characterized by withdrawal symptoms and can involve increased tolerance for the drug. The causes of substance abuse are multiple: some people are high-risk for dependence due to genetic or physiological reasons; others become dependent on drugs to cope with emotional or social problems, or physical pain .
Depressants reduce activity of the central nervous system . The most common depressive drug is alcohol, which calms, induces sleep, decreases inhibitions and fears, and slows reflexes . With continued use, the nervous system accommodates alcohol, requiring increasing amounts to achieve the alcoholic state, and produces withdrawal symptoms. Sedatives are another major category of depressants, notably barbiturates, such as Seconal and Nembutal. Overdoses can be fatal, and withdrawal symptoms are among the most severe for any drug. Anxiolytics (traditionally referred to as tranquilizers) are also sedatives and include the benzodiazepines (Librium, Valium) and meprobamate (Miltown). Many users of these drugs become both psychologically and physically dependent, and their withdrawal symptoms resemble those of barbiturate takers. Taken in combination with alcohol, anxiolytics can be fatal. Anxiolytics are still used in the clinical treatment of anxiety and are the most widely prescribed and used legal drugs. Because they pose little danger of death from overdose, the benzodiazepines have remained popular for the treatment of patients suffering from anxiety. A new member of this class of drug, Xanax, has also been widely used in the treatment of panic disorders and agoraphobia.
Narcotics, such as opiates which include heroin and its derivatives, are drugs with sedative properties; they are addictive and produce tolerance. They have a complex combination of effects, causing both drowsiness and euphoria, and are also pain-killers. Eaten, smoked, inhaled, or injected intravenously, heroin impairs the respiratory system, induces changes in the heart and blood vessels, constipation, and loss of appetite. It is derived from morphine, but is several times more powerful. An overdose of heroin can result in death.
Psychedelics, or hallucinogens , such as marijuana , are consciousness-altering drugs that affect moods, thought, memory , and perception . They can produce distortion of body image , loss of identity, and hallucinations. Usage can produce impaired performance on intellectual and psychomotor tasks, psychoses, and psychological dependence. LSD (lysergic acid diethylamide) is one of the most powerful psychedelic drugs. It can cause bizarre hallucinations , its effects are highly unpredictable, and some users suffer long-term side effects. While low doses of marijuana are considered relaxing and relieve anxiety with minimal health risks, long-term usage in larger amounts may cause major health hazards such as asthma and other respiratory disorders, suppression of the immune system, and heart problems.
Psychostimulants, such as amphetamines and cocaine, are drugs that in moderate or low doses increase mental and behavioral activity. They stimulate alertness, reduce fatigue, increase excitability, elevate moods, and depress appetites. Benzedrine, Dexedrine, Methedrine, (also called "uppers" or "speed"), raise the heart rate and blood pressure, constrict blood pressure, shrink mucous membranes (thus their use as decongestants), and reduce appetite. Many people abuse amphetamines in order to lose weight, remain productive and alert, or to "get high." The symptoms of severe amphetamine abuse can resemble those of paranoid schizophrenia . Cocaine and its derivative, "crack," are both highly addictive and take effect more rapidly than amphetamines. Overdoses, especially of crack, can be fatal, and small doses may induce cardiac arrest or stroke. Cocaine addiction is especially difficult to break.
Two popular stimulants that most people do not consider "drugs" are caffeine and nicotine. Caffeine is found in coffee, tea, chocolate, and many soft drinks. It decreases drowsiness and speeds up thought, but at high doses can produce anxiety and induce tremors. Caffeine is addictive; its withdrawal symptoms include headaches, fatigue,
A crystalline alkaloid derived from the leaves of the South American coca plant, Erythorxylun. Medically, cocaine can be used as a local aesthetic because it interrupts the conduction of the nerve impulses, particularly in the mucous membranes of the eyes, nose and throat. Illegally, cocaine is widely abused. As powered cocaine hydrochloride, it is usually diluted with some other substance, such as aspirin, cornstarch lactose, or talc, and sucked into the nostrils or dissolved in water and injected intravenously. When cocaine is sniffed, it travels from the nasal tissue to the bloodstream and then to the brain, affecting the user within two or three minutes, and if injected, within 15 seconds. Its physiological effects include dilated pupils; elevated heart rate, blood pressure, and body temperature; rapid breathing; and an increased appetite. The drug may also augment norepinephrine and dopamine activity—an effect similar to the of amphetamines—and stimulate the cortex of the brain. Cocaine produces a quick but short "rush," characterized by temporary feelings of euphoria, self-confidence, well-being, and optimism, and hallucinations can also be present. The drug's pleasant effects peak in about 20 to 40 minutes and subside after about a hour, followed by a depression that induces a craving for the drug.
Cocaine can also be converted into a solid from by separating it from its hydrochloride base. This from, commonly known as "crack" cocaine, produces a high that is particularly fast and intense. It is extremely addictive, inducing constant cravings that can cost up to $500 a day to satisfy. Crack cocaine is usually smoked in a pipe or mixed with tobacco in a cigarette. As it has become cheaper to produce, its cost has dropped, and now crack cocaine costs less than one-fifth as much as regular cocaine.
Cocaine is a potent drug, and habituation and dependence may occur very quickly with its abuse. Cocaine users first become psychologically addicted to the drug, as the artificially induced optimism and confidence they feel helps them to cope with daily stresses. Soon, the cocaine user becomes physically addicted as well and often develops a secondary addiction to a depressant, such as alcohol or heroin, to help him or her "come down" from the drug's effects and to induce sleep. When taken internally in any form, cocaine has a highly toxic effect on the central nervous system. Frequent and/or long-term abuse of cocaine may cause over activity, loss of appetite, nausea, heart problems, seizures, comas, strokes, and permanent brain damage. It can also precipitate delusional psychotic disorders.
Withdrawal from habitual cocaine abuse is characterized by severe physical and emotional discomfort and may last several weeks. Symptoms include muscle pains and spasms, and decreased energy levels and mental functioning. It is very difficult to withdraw from the drug without professional help. An overdose of cocaine stimulate the spinal cord, and may result in convulsions, depression of the entire nervous system, respiratory failure, and death. In the past 50 years, the incidence of cocaine among Americans has risen dramatically (although there has been a slight decrease since the mid-1980s). A 1988 survey found that one in ten people had used the drug with the number rising to one in four for adults between the ages of 18 and 25.
craving, and shakiness. They appear within 12 to 24 hours from the last intake, peak at around 48 hours, and continue for a week. Nicotine, the psychostimulant in tobacco, has a powerful effect on the autonomic nervous system . While some claim that nicotine addiction is more psychological than physical, it is associated with definite withdrawal symptoms, including cravings, restlessness, irritability, and weight gain. It can cause lung cancer, heart attack, respiratory disorders, and stroke. When used by pregnant women, it can harm their unborn children in a number of ways.
Certain classes of psychoactive drugs are used clinically to treat depression, mania , anxiety, and schizophrenia. Therapy for severe mental disorders was transformed in the 1950s with the discovery of neuroleptics (antipsychotics), which reduced psychotic symptoms, including delusions, paranoid suspicions, confusion, incoherence, and hallucinations. Phenothiazines, notably chlorpromazine, Thorazine, and Haldol, are the most commonly used antipsychotic drug.
Another drug, clozapine (Clozaril), has effects similar to those of phenothiazines but without the long-term side effect of movement disorders that afflicts at least 25 percent of phenothiazine users. However, about two percent of clozapine users are at risk for a different problem—agranulucytosis, a fatal blood disorder, and all patients who take the drug must be tested regularly for this side effect.
Antidepressants , a second class of therapeutic drugs, reduce symptoms of depression (depressed mood , fatigue, appetite loss, sleep disorders ) in a majority of users. There are several types of antidepressants, including monoamine oxidase inhibitors (MAO-I), which can also relieve panic attacks; tricyclic antidepressants, which seem to be more effective for many patients; and a "second generation" of serotonin-related antidepressants. The best-known drug of this type, Prozac (fluoxetine), has become the most widely prescribed antidepressant in the United States due to its combination of effectiveness and lack of side effects. It also helps sufferers from obsessive-compulsive disorder . The drug lithium is used to relieve episodes of both mania and depression in patients with bipolar disorder .
See also Alcohol dependence and abuse