Drugs cause physical and emotional dependence. Users may develop an
overwhelming craving for specific drugs, and their bodies may respond
to the presence of drugs in ways that lead to increased drug use.
. Regular users of drugs develop _tolerance_, a need to take
larger doses to get the same initial effect. They may respond by
combining drugs--frequently with devastating results. Many
teenage drug users calling a national cocaine hotline report
that they take other drugs just to counteract the unpleasant
effects of cocaine.
. Certain drugs, such as opiates and barbiturates, create _physical
dependence_. With prolonged use, these drugs become part of the
body chemistry. When a regular user stops taking the drug, the
body experiences the physiological trauma known as _withdrawal_.
. _Psychological dependence_ occurs when drug taking becomes the
center of the user's life. Among children, psychological
dependence erodes school performance and can destroy ties to
family, friendships, outside interests, values, and goals. The
child goes from taking drugs to feel good, to taking them to
keep from feeling bad. Over time, drug use itself heightens the
bad feelings and can leave the user suicidal. _More than half of
all adolescent suicides are drug-related._
. _Drugs and their harmful side effects can remain in the body long
after use has stopped._ The extent to which a drug is retained
in the body depends on the drug's chemical composition, that is,
whether or not it is fat-soluble. Fat-soluble drugs such as
marijuana, phencyclidine (PCP), and lysergic acid (LSD) seek out
and settle in the fatty tissues. As a result, they build up in
the fatty parts of the body such as the brain. Such accumulations
of drugs and their slow release over time may cause delayed
effects (flashbacks) weeks and even months after drug use has
stopped.