Introduction
Cannabis use in Australia is most common among young adults (20-29 years) and adolescents (14-19 years). Evidence suggests that higher proportions of people are beginning to use cannabis in their teens.
The younger a person is when they start using cannabis the greater the chance that they may become a regular user of cannabis. Regular use of cannabis at a young age is a risk factor for dependence and health problems. One of the greatest concerns about cannabis use by young people is the link between cannabis use and mental health problems, such as depression, anxiety and psychotic disorders.
This fact sheet provides information about the link between cannabis use and mental health problems.
What is cannabis?
Cannabis is a drug that comes from the Cannabis sativa plant. The active chemical in cannabis is delta-9 tetrahydrocannabinol (THC). When cannabis is used, THC is absorbed into the bloodstream and carried to the brain, producing the "high" feeling. The THC molecules affect a number of areas of the brain, including those that control balance, perception of time, sound and colour, and glucose craving.
What is psychosis?
Psychosis is a cluster of symptoms characterised by delusional thoughts, hallucinations and impaired reality. Psychosis is a symptom of a mental illness, such as schizophrenia.
What is "cannabis psychosis"?
Cannabis use may cause symptoms similar to those observed in psychotic disorders, such as schizophrenia. This type of effect usually occurs as a result of the use of a large amount of cannabis at one time, and stops once cannabis use stops. These symptoms occur because THC stimulates increased production of dopamine, a neurotransmitter that is thought to be involved in psychotic disturbances.
Does cannabis cause schizophrenia?
It has been suggested that heavy cannabis use can cause mental illness such as schizophrenia, but despite significant increases in cannabis use in Australia during the past 30 years, levels of schizophrenia in the population have not increased.
There is mounting evidence that regular cannabis use increases the likelihood of psychotic symptoms occurring in an individual who is vulnerable due to a personal or family history of mental illness. Research suggests that susceptible individuals who avoid cannabis have a 25 per cent chance of developing psychosis, whereas susceptible individuals who smoke cannabis have a 50 per cent risk. It appears that the more cannabis an individual smokes, and the earlier they start, the worse the outcome.
There is some evidence that people with schizophrenia who use cannabis tend to have their first psychotic episode at a younger age than people with schizophrenia who do not use cannabis. Cannabis appears to make psychotic symptoms worse and lowers the chances of recovery from a psychotic episode for those with schizophrenia.
Does cannabis cause depression and anxiety?
Research indicates that there is an association between cannabis use and depression; however, this seems to be influenced by childhood and family factors, other drug use and peer relationships. There is mixed evidence about the link between cannabis use and anxiety disorders, but when other factors, such as childhood and family experiences, are considered, it appears that this link does not exist.
Cannabis use and suicide
There is reason to believe that heavy cannabis use may pose a small risk of suicide.
What you should do
People with a family or personal history of psychotic illness should avoid using cannabis. If you are experiencing feelings of depression you should contact your general practitioner or a health professional.
More information
For more information on drugs and drug prevention contact the DrugInfo Clearinghouse on tel. 1300 85 85 84 , email druginfo@adf.org.au, or see our website www.druginfo.adf.org.au.