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Information on Alcohol

7. Cannabis


The universal term cannabis is used to identify the psychotropic product from the plant Cannabis sativa.

Cannabis sativa is one of man's oldest cultivated plants, being used for its fibrous qualities (hemp) as well as its perceived medicinal properties.


The pharmacologically active compounds in cannabis are termed cannabinoids. The major active isolate in cannabis has been identified as D9 tetrahydrocannabinol (THC). As it is lipid soluble, it may remain in the body tissues for many days after a single dose.

Recent studies have documented a number of health, social and psychological problems related to the regular use of cannabis. Major health concerns revolve around the knowledge that the cannabis of today is markedly (10-15 times) stronger than the cannabis used in the late 1960s and early 1970s. Consequently, previous studies examining the health and psychological risks associated with cannabis use, may not be valid today.

Pharmacologic effects also differ according to the method of consumption. If cannabis is smoked a 'high' is attained much more quickly. In contrast, the effects of cannabis taken orally are much less potent, although more long-lasting. Additive effects are observed with alcohol and other CNS depressants, but no clear interaction has been noted with stimulants.


The major component of cannabis (THC) is fat soluble, which means it can remain for long periods in the fatty tissues of the body. Such lipid soluble drugs tend to leave the blood stream quickly and distribute themselves to fatty tissues, such as the brain and cell membranes

Since THC becomes stored in body tissues and is only released into the blood stream over a period of days or weeks, accumulation of THC may occur. As a result of this accumulation, regular cannabis users may be under the influence of cannabis at any time, and be unaware of the dangers of this.

Another concern is the possible accumulation of THC in the brain, which may in time result in brain damage.


  • Feelings of self confidence, euphoria, well being and relaxation
  • Altered perception of time and space, and heightened perceptions of taste, smell, touch, and hearing
  • Dissociation of ideas
  • Difficulties with concentration and memory
  • Other cognitive impairment
  • Psychomotor impairment
  • Delusions and hallucinations.


  • Young adolescents - particularly males
    • a documented concern is the harmful effects of cannabis use on the maturing process of adolescents
  • Persons with a predisposition to schizophrenia and mental illness
  • Those of lower socioeconomic status and fewer years of formal schooling
  • Young people with friends who are illicit drug users.


  • Reproductive effects
  • Respiratory effects
  • Cardiovascular effects
  • Immunity
  • Neuropsychiatric complications
  • Social problems

Reproductive effects

Respiratory effects

  • Cannabis is known to be both mutagenic and carcinogenic as well as destructive to lung parenchyma and epithelial cells
  • Lung cancer
    • risk comparable to smoking tobacco
    • since cannabis smoke is inhaled deeply, held for much longer and contains more tar than tobacco, the adverse effects are greater. As a result, smoking 2-3 cannabis cigarettes may carry the same risk of lung damage as smoking a whole packet of tobacco cigarettes.
  • Cancer of the upper respiratory and digestive tracts
  • Head and neck cancer
  • Emphysema
  • Increased susceptibility to respiratory infections (eg chronic bronchitis, sinusitis, asthma and rhinopharyngitis)
  • Mild airway obstruction.

Cardiovascular effects

  • Cannabis inhalation results in an increase in heart rate, blood pressure and conjunctival injection. Persons with hypertension, cerebral vascular disease and ischaemic heart disease may be at increased susceptibility to these effects.


  • Mild impairment of immunity and immune reactions: clinical significance unclear.

Neuropsychiatric complications

  • Impairs motor coordination, short-term memory, tracking ability, sensory functions and learning ability
  • Headaches and dizziness
  • Adverse reactions (occur more frequently in individuals who are under stress, anxious, depressed, or who are predisposed to functional psychoses)
    • mild anxiety
    • panic and paranoia, confusion and delusional thinking
    • acute psychosis, detachment from reality, hallucinations or illusions
    • paranoid schizophrenia (it is not yet known whether cannabis precipitates schizophrenia, or if those with schizophrenia are more likely to be attracted to using cannabis as a form of self medication)
    • dissociation of ideas, distortions of time and space, compulsiveness
    • sleeplessness
    • depression
    • amotivational syndrome
    • cannabis use has been associated with apathy and antisocial behaviours
    • observed inability of users to incorporate and use new skills, which may delay the maturation process
    • some adolescents who use cannabis have been observed to be devoid of the drive and energy normally seen in adolescents
    • impaired ability to memorise and concentrate
    • diminished scholastic and/or job performance
    • introversion

It is not yet understood whether cannabis use causes the above problems, or whether they occur as a symptom of an underlying disorder such as mental illness, or social problems revolving around the family, friends or school.

Social problems

  • Truancy can cause problems at school which may eventuate in dropping out of school at an early age and possible delinquent behaviour
  • Deterioration of academic or job performance
  • Legal problems
  • Ability to operate machinery, or drive a car etc. is impaired
  • Loss of job or problems at work resulting from cannabis use.



Signs and symptoms of tolerance, and also dependence, may persist for months in very heavy users. THC accumulates in adipose tissue and can take weeks or months to be totally excreted.


Frequent use of cannabis can produce mild physical dependence and, as a consequence, withdrawal symptoms.


The withdrawal usually starts several hours after cessation of use, is usually mild and is over within a matter of days for most users. Some of the symptoms experienced may include:

  • anxiety
  • depression
  • sleep and appetite disturbances
  • irritability
  • tremors
  • perspiration
  • nausea
  • muscle twitching
  • restlessness
  • weight loss
  • gastrointestinal upsets.

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