Almost 30 million Americans were considered current illicit drug users in 2014 according to a national survey, as drugs alter brain chemistry and perceptions. Drug abuse impacts neurotransmitters like dopamine, serotonin, GABA, and norepinephrine which regulate functions like mood, pleasure, and stress responses. The brain stem, limbic system, and cerebral cortex are all affected by drug abuse according to the National Institute on Drug Abuse. Regular drug use leads to dependence and withdrawal symptoms and can cause addiction by disrupting brain chemicals and circuitry.

1. Almost 30 million Americans were considered to be current illicit drug users in 2014,
meaning that they had abused drugs within the month leading up to that
year’s National Survey on Drug Use and Health (NSDUH). Drugs interact with the
brain and body to alter moods, emotions, and behaviors by changing brain chemistry
and a person’s perceptions, and by impacting how individuals interact with the world
around them.
Mind-altering drugs may slow down or speed up the central nervous system and
autonomic functions necessary for living, such as blood pressure, respiration, heart
rate, and body temperature. Levels of some of the brain’s chemical messengers, or
neurotransmitters, are also impacted by drug abuse, including:
 Dopamine: This neurotransmitter regulates moods, enhances pleasure, and is
involved with movement, reward and reinforcing behaviors, motivation, and
attention.
 Serotonin: This neurotransmitter is responsible for stabilizing moods and
regulating emotions.
 Gamma-aminobutyric acid (GABA): GABA acts as a natural tranquilizer,
mitigating the stress response and lowering anxiety levels as well as slowing
down functions of the central nervous system.
 Norepinephrine: Similar to adrenaline, norepinephrine is often called the
“stress hormone,” as it speeds up the central nervous system in response to the
“fight-or-flight” response. It also homes focus and attention while increasing
energy levels
Regions of the brain are disrupted by drug abuse, as the National Institute on Drug
Abuse(NIDA) reports that the brain stem, limbic system, and cerebral cortex are all
affected. The brain stem controls life-sustaining functions, including sleeping,
breathing, and heart rate, while the limbic system holds the brain’s reward circuitry
and helps to control emotions and the ability to feel happiness. The cerebral cortex is
considered the “thinking center” of the brain, managing problem-solving, planning,
and decision-making abilities as well as helping people to process information
provided by their senses.
The more often drugs are used, the more they will impact brain chemicals and
circuitry, which can lead to drug dependence and withdrawal symptoms when the
drugs process out of the body. Drug cravings, dependence, and withdrawal symptoms,
coupled with a loss of control over use, are signs of addiction.
The American Society of Addiction Medicine (ASAM) defines addiction as a disease
affecting brain chemistry and circuitry, which then leads to compulsive drug-seeking

2. and using behaviors. In 2014, nearly 22 million Americans battled addiction, NSDUH
reports.
Marijuana
Marijuana is the most regularly used illicit
drug in the United States, and its use is especially common among adolescents and
young adults, NIDAreports. The psychoactive chemical in marijuana, delta-9-
tetrahydrocannabinol (TCH), interacts and binds with cannabinoid receptors in the
brain, producing a mellowing and relaxing effect.
Regions of the brain with high concentrations of cannabinoid receptors are heavily
impacted. One such part of the brain, the hippocampus, manages short-term memory,
meaning that marijuana use can impede recollection of recent events. Additional
regions of the brain that are impacted include the cerebellum and basal ganglia, which
help to control coordination and involuntary muscle movements respectively. When
someone abuses marijuana, impaired motor skills, mood alterations, distorted time
and sensory perception, decreased memory, and trouble thinking clearly and solving
problems are all common short-term side effects. Marijuana also interferes with levels
of dopamine in the brain, causing the euphoric “high” that users document.
Marijuana also has several long-term side effects on the brain, which are especially
prevalent in individuals who use the drug before the brain is fully
developed. NIDA warns that marijuana use in adolescence, and continued on into
adulthood, may result in a loss of IQ points that are not recoverable even with
abstinence. Also, initiating marijuana use before turning age 18 raises the risk for
addiction as an adult. As many as 30 percent of those who use marijuana will suffer
from addiction to the drug, and the risk is increased 4-7 times when use begins before
the age of 18. As a person ages, neurons in the hippocampus are naturally lost,
and marijuana use may speed up this process, leading to memory problems. Impaired
coordination, learning issues, and sleep problems can result from long-term marijuana
use and its impact on the brain.

3. NIDA also reports on the possible link between marijuana use and the onset of
psychosis and psychiatric disorders like schizophrenia in those who are genetically
vulnerable. Breathing and respiration problems, chronic cough, and bronchitis are
additional possible consequences of chronic marijuana smoking. Marijuana use can
also disrupt heart rhythm and normal cardiac functions.