Does cannabis cause psychosis?
Long story short, sort of!
The majority of people who use cannabis are unlikely to develop any lasting mental illness as a result of its use. However, this does not mean that there isn’t a risk!
What researchers have gathered from the results of their studies is that cannabis can potentially cause psychosis, but the most prevalent association is within a select group of people who are naturally vulnerable. Specifically, heavy users of cannabis within an at-risk population, such as those who have a family history of serious mental illness, are more vulnerable to developing psychosis from cannabis use. Furthermore, those with an existing psychotic disorder may have a substandard long-term outcome.
Adolescent users are at a greater risk
Adolescent use of cannabis has been associated with an earlier onset of psychosis, especially in those who are at a greater risk for psychosis, compared to the general population. The reason for this is further explained on THC and young brains. In short, your brain is not fully developed, and is therefore more sensitive to drug exposure.
The risk with cannabis use and development of psychosis varies from an estimated 4x – 12x depending on factors such as family history of mental illness, age at which cannabis use starts and THC content of the cannabis.
The estimated average age of initiation in Canada ranges from 17.2 years to 19.7 years
https://www.canada.ca/en/services/health/publications/drugs-health-products/canadian-cannabis-survey-2018-summary.html
Specifically, regular cannabis use in adolescence:
- is linked the development of a chronic life-long psychotic disorder in at-risk individuals
- is associated with an earlier age of onset of psychosis
- can complicate and/or prevent recovery in individuals already diagnosed with a psychotic disorder
Am I considered to be a part of the at-risk population?
Possibly. There is really no way at present to identify who will have a mental health crisis with cannabis use.
It is believed that there is a certain subset of the general population that are at a higher risk of long-term psychosis with cannabis use. Research shows that at-risk population is still not known, however epidemiology data shows that environmental factors like childhood trauma, genetic factors and other biological factors can increase the risk of developing psychotic disorders.
Other ideas are that people who have a stronger predisposition to psychosis are at a greater risk, such as those who have a family history of psychosis or have had a previous psychotic experience.
Age is another big factor, as mentioned above, as teenagers are more at risk than adults. Which is important because the daily use of cannabis during adolescence increases the risk of long-term dependence on cannabis from 9% to a range of 25-50%.
Finally, continued cannabis use may result in bad long-term outcomes in individuals with pre-existing psychotic disorders.
Moral of the story..
- People who use cannabis in their early teenage years (<age 15) are at greater risk of developing psychosis, at a younger age, and later in life.
- Cannabis use has been shown to trigger and worsen psychosis in some young people. They are also likely to experience their first symptoms at a younger age.
- The earliest onset is associated with higher THC cannabis strains; an average of 6 years earlier onset.
Overall, this knowledge has led to the development of lower risk cannabis use guidelines that strongly suggest starting cannabis use later in life.
If you are under the age of 25 or have been previously diagnosed with a mental illness, use cannabis with caution.
Starting cannabis after age 18 is associated with a lower risk of developing psychosis than starting by age 15. However, our best evidence is that waiting until your brain is fully developed (age 21 to 25) is your best defence against the risk of developing psychosis with cannabis use.