Psychoactive Drugs

The use of psychoactive drugs is a common method for altering consciousness.
These drugs are chemical substances that act on the brain to create
psychological effects and are typically classified as depressants, stimulants,
narcotics (opiates), hallucinogens, or antipsychotics. Several drugs, such as
nicotine, caffeine, and alcohol, are so much a part of the lifestyle in modern
society that users may not even think of them as drugs. The use of many psychoactive
drugs can lead to physical or psychological dependence or addiction,
as the body/mind develops a physiological/psychological need for the
drug. The body can also build up a tolerance for a drug, which means that
higher and higher doses are necessary to produce the same effects. Once
addiction has been established, discontinuing the use of the drug can lead
to withdrawal symptoms, such as nausea, fever, convulsions, and hallucinations,
among others, which can sometimes be fatal.
The type of altered state produced by a psychoactive drug depends on
the class to which the drug belongs. Depressants, such as alcohol, barbiturates,
and tranquilizers, depress central nervous system functioning and
usually produce relaxation, anxiety reduction, and—eventually—sleep. Narcotics
(opiates), such as heroin, morphine, and codeine, depress activity in
some areas of the cortex but create excitation in others, producing feelings
of euphoria and providing relief from pain. Stimulants, such as amphetamines,
cocaine, caffeine, and nicotine, stimulate central nervous system
activity, producing feeling of alertness and euphoria and lack of appetite.
Hallucinogens, such as lysergic acid diethylamide (LSD), mescaline, and psilocybin,
can produce hallucinations, delusions, exhilaration, and, in some
cases, quasi-mystical experiences.