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Subject: Effects of Marijuana
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eduganja 12.04.09 - 08:19pm
Cannabis produces euphoria and relaxation, perceptual
alterations, time distortion, and the intensification of
ordinary sensory experiences, such as eating, watching
films, and listening to music.2 When used in a social setting it may produce infectious laughter and
talkativeness. Short-term memory and attention, motor
skills, reaction time, and skilled activities are impaired
while a person is intoxicated.2
The most common unpleasant side-effects of
occasional cannabis use are anxiety and panic reactions.2
These effects may be reported by nave users, and they
are a common reason for discontinuation of use; more
experienced users may occasionally report these effects
after receiving a much larger than usual dose of THC.2
Cannabis smoking or ingestion of THC increases heart
rate by 2050% within a few minutes to a quarter of an
hour; this effect lasts for up to 3 h.2 Blood pressure is
increased while the person is sitting, and decreased while
standing.2 These effects are of negligible clinical
significance in healthy young users because tolerance
develops to them.2
The acute toxicity of cannabinoids is very low.2 There
are no confirmed published cases worldwide of human
deaths from cannabis poisoning, and the dose of THC
required to produce 50% mortality in rodents is extremely
high compared with other commonly used drugs.2
Psychmotor effects and driving
Cannabis produces dose-related impairments in cognitive
and behavioural functions that may potentially impair
driving a motor vehicle or operating machinery.6 These
impairments are larger and more persistent for difficult
tasks that depend on sustained attention.6 The most
serious possible consequence of acute cannabis use is a
road-traffic accident if a user drives while intoxicated.2
The effects of recreational doses of cannabis on driving
performance in laboratory simulators and standardised
driving courses have been reported by some researchers
as being similar to the effects when blood alcohol
concentrations are between 007% and 010%.2
However, studies of the effects of cannabis on driving
under more realistic conditions on roads have shown
much more modest impairments,7,8 probably because
cannabis users are more aware of their impairment and
less inclined to take risks than alcohol users.7,8
Results of epidemiological studies of road-traffic
accidents are equivocal because most drivers who have
cannabinoids in their blood also have high blood alcohol
concentrations.2 In two studies with reasonable numbers
of individuals who had only used cannabis, there was no
clear evidence of increased culpability in these drivers.9
The separate effects of alcohol and cannabis on
psychmotor impairment and driving performance in
laboratory tasks are roughly additive,9 so the main effect
of cannabis use on driving may be in amplifying the
impairments caused by alcohol, which is often used with the drug.Summary of adverse effects of cannabis
Acute effects
Anxiety and panic, especially in nave users.
Impaired attention, memory, and psychmotor performance while
intoxicated.
Possibly an increased risk of accident if a person drives a motor
vehicle while intoxicated with cannabis, especially if cannabis is
used with alcohol.
Increased risk of psychotic symptoms among those who are
vulnerable because of personal or family history of psychosis.
Chronic effects (uncertain but most probable)
Chronic bronchitis and histopathological changes that may be
precursors to the developmentof malignant disease.
A cannabis dependence syndrome characterised by an inability to
abstain from or to control cannabis use.
Subtle impairments of attention and memory that persist while
the user remains chronically intoxicated, and that may or may
not be reversible after prolonged abstinence.
Possible adverse effects (to be confirmed)
Increased risk of cancers of the oral cavity, pharynx, and
oesophagus; leukaemia among offspring exposed in utero.
Impaired educational attainment in adolescents and
underachievement in adults in occupations requiring high-level
cognitive skills.
Groups at higher risk of experiencing these adverse effects
Adolescents with a history of poor school performance, who
initiate cannabis use in the early teens, are at increased risk of
using other illicit drugs and of becoming dependent on cannabis.
Women who continue to smoke cannabis during pregnancy may
increase their risk of having a low-birthweight baby.
People with asthma, bronchitis, emphysema, schizophrenia, and alcohol and other drug dependence, whose illnesses may be
exacerbated by cannabis use *
