International Research Compendium - Drug Free Australia

A consequence of long term marijuana use is the dependence on the psychoactive
effects of THC and a withdrawal syndrome on cessation of use. A distinctive
marijuana withdrawal syndrome including restlessness, irritability, mild agitation,
insomnia, sleep disturbance, nausea and cramping has been identified, but it is
relatively mild and short-lived.
Marijuana addictions are increasing
Today’s cannabis is 5 to 10 times as strong as it was in the 1970s.
The number of adults using marijuana in the U.S. had remained the same between
1992 and 2002, but the number of adults addicted to the drug had increased 25%.
The 2002 DAWN
survey showed a dramatic increase in marijuana-related hospital emergency room
visits. Data showed that in 1992 there were 45 treatment admissions for marijuana
use per 100.000 people aged 12 or older. This number more than doubled to 93
admissions by 1997 and in 2002 was 118. Marijuana use also leads to more
teenagers entering drug treatment in the U.S. than does the use of all other drugs
combined, including alcohol.
Early use and positive experiences in early use increase the risk for cannabis
dependence.
Once they’re dependent, teens often tumble into truancy, crime and depression.
They can’t concentrate. They don’t go to school. They get totally detached from life.
Because marijuana distorts perception, impairs judgement and verbal skills,
compromises the ability to learn and remember information, induces memory loss
and causes attention deficits, the more a person uses marijuana, the more he or she
is likely to fall behind in performing an intellectual job or social skills.
Marijuana use increases tendencies toward stealing, fighting en violence.
Marijuana use contributes to risky sexual behaviours that increase the likelihood of
disease and unwanted pregnancies.
Exposure to cannabis in the womb could cause children to experience learning
difficulties and hyper reactivity.
Cocaine
Cocaine blocks the reuptake of dopamine by the neurons that originally released it.
Cocaine binds to the dopamine transporters. In this way, cocaine blocks its ability to
transport dopamine from the synapse. This prevents the axon terminals from
retrieving dopamine from the synapse. Dopamine is now trapped in the synapse,
stimulates and restimulates dopamine receptors.
A run of cocaine use ends with a reversal of the user’s initial experience: euphoria is
followed by depression, energy by exhaustion, pleasure by malaise. Cocaine users
not only feel terrible after a run of cocaine use, they find they are unable to
experience life’s normal pleasures. Their brain’s pleasure system has been
overstimulated and exhausted by cocaine use, which is a depletion of dopamine. The
brain requires weeks or even months to re-establish a normal equilibrium in the
synapses of the dopamine transmitting neurons, and there is a risk of producing a
lifelong state of diminished ability to experience normal pleasures.
Structural changes in neurons have also been seen following sensitisation to
cocaine, such as a marked increase in the number of dendritic spines of the neurons
of the Nuc. Accumbens and the prefrontal cortex.
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