Drug Abuse, Addiction and the Brain
By
Dr.Fourkan Ali
Drugs are chemicals that tap into the brain's communication
system and disrupt the way nerve cells normally send, receive, and process
information. There are at least two ways that drugs are able to do this: by
imitating the brain's natural chemical messengers, and/or overstimulating the
"reward circuit" of the brain.
Some
drugs, such as marijuana and heroin, have a similar structure to chemical messengers, called
neurotransmitters, which are naturally produced by the brain. Because of this
similarity, these drugs are able to "fool" the brain's receptors and
activate nerve cells to send abnormal messages.
Other
drugs, such as cocaine or methamphetamine, can cause the nerve cells to release abnormally
large amounts of natural neurotransmitters, or prevent the normal recycling of
these brain chemicals, which is needed to shut off the signal between neurons.
This disruption produces a greatly amplified message that ultimately disrupts
normal communication patterns.
Nearly
all drugs, directly or indirectly, target the brain's reward system by flooding
the circuit with dopamine. Dopamine is a neurotransmitter present in regions of
the brain that control movement, emotion, motivation, and feelings of pleasure.
The overstimulation of this system, which normally responds to natural
behaviors that are linked to survival (eating, spending time with loved ones,
etc), produces euphoric effects in response to the drugs. This reaction sets in
motion a pattern that "teaches" people to repeat the behavior of
abusing drugs.
As
a person continues to abuse drugs, the brain adapts to the dopamine surges by
producing less dopamine or reducing dopamine receptors. The user must therefore
keep abusing drugs to bring his or her dopamine function back to ''normal'' or
use more drugs to achieve a dopamine high.
Long-term
drug abuse causes changes in other brain chemical systems and circuits, as
well. Brain imaging studies of drug-addicted individuals show changes in areas
of the brain that are critical to judgment, decision-making, learning and
memory, and behavior control. Together, these changes can drive an abuser to
seek out and take drugs compulsively -- in other words, to become addicted to
drugs.
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