AMA Youth Brochure Series: Cannabis and your health

1 Jan 2008

What is Cannabis?

Cannabis is the most common illicit drug used in Australia and is derived from the Indian Hemp plant. Other names for Cannabis include marijuana, hashish (hash), dope, mull, grass, pot, weed, ganja and skunk.

Cannabis is a complex mixture of many compounds of variable concentration.

The main active ingredient in Cannabis is called delta-9 tetrahydrocannabinol (THC). THC is rapidly absorbed into the bloodstream and taken to the brain, producing a ‘high’ and altering mood and perception. The strength of Cannabis can vary depending on the THC content.

The two main forms of Cannabis are:

  • Marijuana - which consists of dried plant material and is usually smoked in a ‘joint’ or through a bong; and
  • Hashish - which is made up of hard chunks of dried Cannabis resin and can be eaten in food such as biscuits and cakes.

Both Marijuana and Hashish can be mixed with tobacco for smoking or added to food.

The effects of Cannabis

The effect of any drug depends on a variety of factors. These include the amount taken, weight of the user, past drug experiences, the method in which it is used and the circumstances in which the drug is taken (the place, feelings of the user, people present, whether alcohol or other drugs and medications are taken at the same time). These factors will vary from person to person and from time to time.

Short term effects of small doses on mental health can include:

  • acute transient psychotic symptoms
  • exacerbation of pre-existing psychotic symptoms

The most common short term effects of a small dose of Cannabis are:

  • impaired balance and coordination;
  • a ‘high’ - with a tendency to talk and laugh more than usual;
  • difficulties with memory retention and retrieval;
  • an increase in heart rate;
  • decreased inhibitions, such as being more likely to engage in risky behaviour such as unsafe sexual practice, and dangerous driving; and
  • if smoked, the effects on the lungs are similar to tobacco smoke. This can make asthma and other respiratory problems worse

A small number of people who use Cannabis are very sensitive to its effects. The effects can take the form of agitation; anxiety and panic; a sense of loss of control over thoughts, feelings and sensations; feelings of suspiciousness and paranoia. In a situation like this, it is important for people not to be left on their own and be supported and reassured. The effects can last up to 6-8 hours. Medical help should be sought.

Short term effects of large doses...

The most common short term effects of a large dose are:

  • hallucinations;
  • vomiting;
  • feelings of panic or intense anxiety;
  • blacking out;
  • changes in perception of time, sound, colour, distance, touch and other sensations;
  • restlessness; and
  • confusion.

Long term effects...

If Cannabis is taken on a regular basis over a long period of time then the following health problems may be experienced:

  • tolerance - more of the drug is needed to produce the same effect;
  • increased risk of damage to lungs and lung functioning, including an increased risk of lung cancer;
  • a decrease in motivation;
  • a decrease in concentration;
  • difficulties with memory and ability to learn new tasks;
  • decreased sex drive;
  • lowered sperm count in men; and
  • irregular menstrual cycles in women.

Pregnant Women

Women who are pregnant and continue to smoke cannabis during pregnancy, as with cigarette smoking, may have lower birth weight babies.

Driving and operating machinery under the influence of cannabis

Cannabis increases the risk of having an accident due to slow reaction time, blurred vision, poor judgement and drowsiness. These effects can last several hours and vary according to the quantity and quality of THC content and are increased by use of alcohol.

Cannabis & mental illness...

There is strong and increasing evidence to show that any use of Cannabis by people who have had a mental illness is unwise and should be discouraged. When people are ‘stoned’ they can forget to take their medications and Cannabis makes delusions, mood swings and hallucinations worse. This is especially so with feelings of paranoia. In these cases Cannabis can trigger off further bouts of illness and or destabilise the treatment of illness. Many severely ill people admitted to psychiatric hospitals have been using Cannabis, which has contributed to their admission.

Cannabis use is associated with poor outcomes in the case of existing schizophrenia, and may precipitate major mental illness in those with a predisposition. It appears that using larger amounts of cannabis at an earlier age, and having a genetic predisposition, increases the risk of developing schizophrenia.

How long do the effects of Cannabis use last?

  • intoxicating effects occur within seconds to minutes, and can last for three hours;
  • for large doses the effects last longer;
  • effects on thinking and co-ordination can last up to 24 hours;
  • short term memory loss can last for a number of weeks; and
  • a complete elimination of a single dose can take up to 30 days.

Can users become dependent on Cannabis?

Some regular users can become psychologically dependent on Cannabis. Dependence can negatively affect personal relationships, school and education, employment and many other aspects of a person’s life.

More information & help.

Your family doctor can provide more information, advice or assistance about Cannabis, or they may refer you to other community health centres if necessary.

Information can also be obtained by contacting Alcohol and Drug Information Service (ADIS) in your state or territory.

ADIS offers confidential services 24 hours a day, 7 days a week for anyone with concerns relating to Cannabis, alcohol or other drugs. Further information can also be obtained from the Australian National Council on Drugs booklet - Cannabis: answers to your questions.