Marijuana on the Brain
Researchers have found that THC changes the way in which sensory information gets into
and is acted on by the hippocampus. This is a component of the brain's limbic system that
is crucial for learning, memory, and the integration of sensory experiences with emotions
and motivations. Investigations have shown that neurons in the information processing
system of the hippocampus and the activity of the nerve fibers are suppressed by THC. In
addition, researchers have discovered that learned behaviors, which depend on the
hippocampus, also deteriorate.
Recent research findings also indicate that long-term use of marijuana produces changes
in the brain similar to those seen after long-term use of other major drugs of abuse.
Effects on the Lungs
Someone who smokes marijuana regularly may have many of the same respiratory problems
that tobacco smokers have. These individuals may have daily cough and phlegm, symptoms of
chronic bronchitis, and more frequent chest colds. Continuing to smoke marijuana can lead
to abnormal functioning of lung tissue injured or destroyed by marijuana smoke.
Regardless of the THC content, the amount of tar inhaled by marijuana smokers and the
level of carbon monoxide absorbed are three to five times greater than among tobacco
smokers. This may be due to the marijuana users inhaling more deeply and holding the smoke
in the lungs.
Effects on Heart Rate and
Recent findings indicate that smoking marijuana while shooting up cocaine has the
potential to cause
severe increases in heart rate and blood pressure. In one study,
experienced marijuana and cocaine users were given marijuana alone, cocaine alone, and
then a combination of both. Each drug alone produced cardiovascular effects; when they
were combined, the effects were greater and lasted longer. The heart rate of the subjects
in the study increased 29 beats per minute with marijuana alone and 32 beats per minute
with cocaine alone. When the drugs were given together, the heart rate increased by 49
beats per minute, and the increased rate persisted for a longer time. The drugs were given
with the subjects sitting quietly. In normal circumstances, an individual may smoke
marijuana and inject cocaine and then do something physically stressful that may
significantly increase risks of overload on the cardiovascular system.
of Heavy Marijuana Use on Learning and Social Behavior
A study of college students has shown that critical skills related to attention,
memory, and learning are impaired among people who use marijuana heavily, even after
discontinuing its use for at least 24 hours. Researchers compared 65 "heavy
users," who had smoked marijuana a median of 29 of the past 30 days, and 64
"light users," who had smoked a median of 1 of the past 30 days. After a closely
monitored 19- to 24-hour period of abstinence from marijuana and other illicit drugs and
alcohol, the undergraduates were given several standard tests measuring aspects of
attention, memory, and learning. Compared to the light users, heavy marijuana users made
more errors and had more difficulty sustaining attention, shifting attention to meet the
demands of changes in the environment, and in registering, processing, and using
information. The findings suggest that the greater impairment among heavy users is likely
due to an alteration of brain activity produced by marijuana.
Longitudinal research on marijuana use among young people
below college age indicates those who used have lower achievement than the non-users, more
acceptance of deviant behavior, more delinquent behavior and aggression, greater
rebelliousness, poorer relationships with parents, and more associations with delinquent
and drug-using friends.
Research also shows more anger and more regressive behavior (thumb sucking, temper
tantrums) in toddlers whose parents use marijuana than among the toddlers of non-using