What is cannabis?

Cannabis (marijuana) is a green or grey mixture of dried, shredded flowers and leaves of the hemp plant Cannabis sativa. There are over 200 slang terms for marijuana, including ‘dagga’, ‘pot’, ‘herb’, ‘weed’, ‘boom’, ‘Mary Jane’, ‘gangster’ and ‘chronic’. It is usually smoked as a cigarette (called a joint or a nail) or in a pipe or bong. In recent years, it has appeared in blunts. These are cigars that have been emptied of tobacco and re-filled with marijuana, often in combination with another drug, such as crack. Some users also mix marijuana into foods or use it to brew tea.

Active chemical ingredient

The main active chemical in marijuana is THC (delta-9-tetrahydrocannabinol). In 1988, it was discovered that the membranes of certain nerve cells contain protein receptors that bind THC. Once securely in place, THC kicks off a series of cellular reactions that ultimately lead to the high that users experience when they smoke marijuana. The short-term effects of marijuana use include problems with memory and learning; distorted perception; difficulty in thinking and problem solving; loss of coordination; and increased heart rate, anxiety, and panic attacks.

Cannabis effects may be hereditary

Scientists have found that whether an individual has positive or negative sensations after smoking marijuana can be influenced by heredity. A recent study demonstrated that identical male twins were more likely than non-identical male twins to report similar responses to marijuana use, indicating a genetic basis for their sensations. Identical twins share all of their genes, and fraternal twins share about half.

Environmental factors such as the availability of marijuana, expectations about how the drug would affect them, the influence of friends and social contacts, and other factors that would be different even for identical twins, also were found to have an important effect. However, it also was discovered that the twins’ shared or family environment before age 18 had no detectable influence on their response to marijuana.

Signs of cannabis use

  • rapid, loud talking and bursts of laughter in the early stages of intoxication
  • sleepiness in the later stages.
  • lack of concentration and coordination
  • forgetfulness in conversation
  • inflammation in whites of eyes
  • smell similar to burnt rope on clothing or breath
  • distorted sense of time passage – a tendency to overestimate time intervals
  • a craving for sweets
  • increased appetite
  • use or possession of paraphernalia including roach clip, packs of rolling papers, pipes or bongs

Physical effects of cannabis

  • a faster heartbeat and pulse rate
  • bloodshot eyes
  • dry mouth and throat

(No scientific evidence indicates that marijuana improves hearing, eyesight, and skin sensitivity.)

Other serious side-effects

  • Marijuana use increases the heart rate as much as 50 per cent, depending on the amount of THC taken in.
  • It can cause chest pain in people who have a poor blood supply to the heart – and it produces these effects more rapidly than tobacco smoke does.
  • Scientists believe that marijuana can be especially harmful to the lungs because users often inhale the unfiltered smoke deeply and hold it in their lungs as long as possible. Therefore, the smoke is in contact with the lung tissue for long periods of time, which irritates the lungs and damages the way they work.
  • Marijuana smoke contains some of the same ingredients in tobacco smoke that can cause emphysema and cancer. In addition, many marijuana users also smoke cigarettes or mix marijuana leaves with tobacco. The combined effects of smoking these two substances create an increased health risk.
  • Burnout’ is a term first used by marijuana smokers themselves to describe the effect of prolonged use. Young people who smoke marijuana heavily over long periods of time can become dull, slow-moving and inattentive. These ‘burned-out’ users are sometimes so unaware of their surroundings that they do not respond when friends speak to them, and they do not realise they have a problem.

How does cannabis affect your mind?

Studies of marijuana’s mental effects show that the drug can impair or reduce short-term memory, alter sense of time, and reduce ability to do things which require concentration, swift reactions and coordination, such as driving a car or operating machinery.

A common bad reaction to marijuana is the ‘acute panic anxiety reaction’. People describe this reaction as an extreme fear of ‘losing control’, which causes panic. The symptoms usually disappear in a few hours.

Long-term marijuana abuse

Laboratory studies have shown that animals exhibit symptoms of drug withdrawal after stopping from prolonged marijuana administration. Some human studies have also demonstrated withdrawal symptoms such as irritability, stomach pain, aggression and anxiety after cessation of oral administration of tetrahydrocannabinol (THC), marijuana’s principal psychoactive component. Now, researchers at McLean Hospital in Belmont, Massachusetts, and Columbia University in New York City have shown that individuals who regularly smoke marijuana experience withdrawal symptoms after they stop smoking the drug.

Studies at Columbia University in New York City have demonstrated that, in addition to aggression, marijuana smokers experience other withdrawal symptoms such as anxiety, stomach pain and increased irritability during abstinence from the drug.

Cannabis-induced psychosis

Scientists have found that one in four people carries genes that increase vulnerability to psychotic illnesses if he or she smokes cannabis as a teenager. A common genetic profile that makes cannabis five times more likely to trigger schizophrenia and similar disorders has been identified.


How do I get help for myself or my loved one?

The first step in getting help is finding out whether you have a problem. A trained clinical psychologist can effectively perform a professional assessment, which will identify whether you have any problem areas, and will recommend the treatment most appropriate for you if necessary.

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