Cannabis is the most widely used illicit drug in Australia and is recognised as the third most prevalent drug of dependence following alcohol and tobacco. Cannabis use is increasing among younger age groups. 14.9% of people using cannabis for the first time are aged between 1-19 years. The use of cannabis in adolescence is concerning because it occurs at an important time of transition between childhood and adulthood when brains are still undergoing physiological changes. However, many Australians use cannabis without adverse effects. There is evidence that the strength of cannabis and its active ingredient, THC (the chemical that makes you feel ‘high’), has increased over the past 30 years, however there is conjecture over this. Strong associations are consistently found between mental illness and cannabis use. Evidence shows that those who are most at risk of developing a mental illness with the use of cannabis are those who begin at an early age and those who are vulnerable for sociological reasons, including educational failure, unemployment and crime.
There is a lot of debate around whether cannabis can cause schizophrenia. Evidence shows that cannabis use can trigger schizpohrenia in people who have a predisposition via family history of that mental illness. Evidence further shows that cannabis use in high doses may lead to psychotic symptoms in the short term. However it cannot be considered a major causal factor.