There is considerable discussion currently around cannabis in the community and whether, because it is often seen as a ‘soft drug’, it should be legalised. However, this statement too simplistic and fails to consider the impact of cannabis use on a range of populations.

Research has established that cannabis is the most widely used illicit drug in this country. Only the legal drugs of tobacco and alcohol are used more widely then cannabis. Approximately 10.3% of persons aged 12 years or over reported recent use of cannabis (2010), while ecstasy was the second most commonly reported illicit drug used with 2.9% of people 12 years or over reporting having used ecstasy in the previous12 months.  Tobacco and alcohol are the substances that cause the greatest degree of harm in this country (Drugs in Australia 2010).

There is strong evidence of the relationship between cannabis use and mental illness, particularly in young people. Research suggests that the risk factors associated with cannabis use increases if mental health runs in a family. Long-term cannabis use has been linked to depression, anxiety and psychotic disorders including delusions, hallucinations and disorganised thinking or speech (ADF 2014).

Cannabis use can increase the severity of psychotic illness. A person experiencing a psychotic illness who uses cannabis can increase their psychotic symptoms; increase chance of hospitalisation while their treatment and recovery become more difficult (ADFG 2000).  Research reports that as a person’s cannabis use increases so does the use of other substances both licit and illicit, particularly alcohol (L. Degenhardt et el (2000)

Dr Edmund Sillins et el (2014) in the Lancet Psychiatry Journal reported that there were a number of clear and consistent outcomes from adolescent cannabis use that extend well into adult life. These outcomes included reduced opportunities of completing high school or obtaining a university qualification, together with increased likelihood of cannabis dependence, use of other illicit drugs, and suicide attempts.

The message to be taken from this research is the need to reduce adolescent cannabis use to prevent long-term harm. Strategies to reduce the harm associated with cannabis use:

1. Delay the use of cannabis by adolescence
2. Avoid cannabis use if there is a family history of mental illness
3. Obtain clear and accurate information so you are well informed
4. Encourage professional help
5. Be understanding and patient

As we celebrate Mental Health Week 2014 this week, it’s important that we all understand the flow on effects of a range of behavioural choices to our mental health, illicit drug use being one of these choices.

Dr Dennis Young

CEO Mental Health Association of Queensland

For references and further reading purposes:

• Louisa Degenhardt et el (2000) Louisa Cannabis use and mental health among Australian adults: Findings from the National Survey of Mental Health and Well-Being
• Dr Edmund Silins PhD et al (2014) Young adult sequelae of adolescent cannabis use: an integrative analysis
• Alcohol and drug foundation fact sheet (2014) – Cannabis and mental health

• Factsheet NCPIC (2012) – Cannabis and mental health
• Drugs in Australia (2010) Australian Institute of Health and Welfare Canberra