What is Cannabis?
Cannabis refers to the products of the cannabis sativa plant, also known as marijuana and hashish (depending on which part of the plant is used). Cannabis is widely available for use as a recreational drug. It is commonly taken by mixing with tobacco and smoking as a hand-rolled joint, or by inhaling through a water-cooled pipe called a bong. It may also be cooked in food and eaten.

How many people use Cannabis?
Cannabis is the most widely used illicit drug. A recent study indicated that around 30% of the total population had tried Cannabis at some time. Among people under 35 years of age, around 50% had tried it at some time, and 28% had used it in the last year.

How does Cannabis affect the brain?
Cannabis contains a chemical known as THC for short. THC is a psychoactive substance. This means it travels through the bloodstream to the brain, disrupting its usual functioning and causing certain intoxicating effects. Some of these effects can be pleasant; some are unpleasant. Most of these effects are short-term; some can be long-term.

What are the effects of Cannabis?
Common effects include a feeling of relaxation and well-being; loss of inhibition; increased talkativeness; confused perception of space and time; sedation, and reduced ability to concentrate and remember. Other effects (more common with heavy use) include paranoia, confusion and increased anxiety. With heavy use there may also be hallucinations.

How long do the effects last?
The effects begin within minutes and can last up to several hours. For people with a psychotic illness, or who have a predisposition to such an illness, the effects can be more serious and long-term. Psychotic illnesses are characterised by symptoms such as delusions, hallucinations and thought disorder. When people experience psychotic symptoms, they are unable to distinguish what is real – there is a loss of contact with reality. See also Factsheet 1: Psychosis.

Does Cannabis cause psychotic illnesses like schizophrenia?
Use of Cannabis can cause a condition called Drug-induced psychosis. This usually passes after a few days. However, if someone has a predisposition to a psychotic illness such as schizophrenia, these drugs may precipitate the first episode in what maybe an ongoing condition. There is increasing evidence that regular cannabis use precedes and causes higher rates of psychotic illness.

How does Cannabis affect someone who has a psychotic illness?
Cannabis generally make psychotic symptoms worse and lower the chances of recovery from a psychotic episode. People with a psychotic illness like schizophrenia who use such drugs experience more hallucinations, delusions and other symptoms; they have a higher rate of hospitalisation for psychosis, treatment is generally less effective and recovery more difficult.

So should people with a psychotic illness avoid drugs like Cannabis?
Yes. The consequences can be so serious for the person's health that it is best to avoid drugs such as Cannabis completely. It can be helpful to look at other, healthier ways of relaxing and socialising as an alternative.

How do I find out more?
It is important that you ask your doctor about any concerns you have. SANE Australia also produces a range of easy-to-read publications and multimedia resources on mental illness.

For more information about this topic see:
The SANE Guide to Drugs. Use the Order Form which came with this Factsheet or visit the SANE Bookshop at www.sane.org

SANE Australia . . . Cannabis and psychotic illness

©SANE Factsheet 4
This Factsheet may be freely downloaded, copied and distributed on condition no change is made to the contents. SANE Australia is not responsible for any actions taken as a result of information or opinions contained in the Factsheet. SANE Australia is a business name of Schizophrenia Australia Foundation.
[Version English, 2004]