A new study by the University of Cape Town’s Department of Psychiatry and Mental Health has found that the prevalence of cannabis use in adolescents admitted with mental illness increased after the South African High Court ruling in 2017 to decriminalise cannabis.
The study, “Cannabis use among hospitalised adolescents before and after decriminalisation in South Africa”, was published in the South African Journal of Psychiatry. The study was conducted by registrar Dr Michelle Swartz as part of a Master’s in Medicine in Psychiatry and was supervised by addictions psychiatrist Dr Lisa Dannatt and child psychiatrist Dr Anusha Lachman.
After the high court ruling that decriminalised cannabis use in 2017, there was no specific legislation to protect vulnerable adolescents from the potential harms of cannabis use. Research has found that ongoing cannabis use during adolescence can result in long-term changes in brain function and that early initiation and frequent or heavy use of cannabis can lead to psychopathology.
The study reviewed cannabis use and the clinical profile of adolescents hospitalised for mental health care before and after legislative changes in South Africa. Clinical folders were reviewed of adolescents admitted to the Emergency Psychiatric Unit at Groote Schuur Hospital in Cape Town. The study examined records of 266 adolescents, aged 13-18, admitted in the period between April 2015 to March 2019.
“I found that cannabis was the most reported substance used both pre- and post-ruling, with a 3,7% increase in adolescents who smoked cannabis post-ruling,” says Swartz. This, she adds, aligns with the World Drug Report of 2023, which noted a 21% increase in annual cannabis users over the past decade.
A significantly higher proportion of patients who used cannabis presented with a co-morbid psychotic disorder and cannabis use disorder; both pre- and post-ruling. An increase in adolescent admissions was found post-ruling, possibly due to other societal and policy changes, as well as high rates of crime, violence, poverty and substance abuse in South Africa.
“There was a notable increase in hospitalisations due to cannabis use disorders, attributed to greater acceptance, higher potency, increased frequency of use and legislative changes related to cannabis. Despite an increased proportion of females using cannabis post-ruling, I found that the majority of cannabis users were male,” says Swartz.
“Additional key findings in this study included findings that trauma was a significant stressor for cannabis users regardless of the timing of the legal ruling, with a higher proportion of post-ruling patients reporting trauma, including physical, verbal, sexual abuse and neglect. This aligns with findings from a Cape Town study linking childhood abuse to increased substance use.”
Swartz says the study demonstrates that adolescents remained a vulnerable population to the effects of cannabis, with the increasing prevalence of cannabis use in adolescents admitted with mental illness.
“While the findings in this study are limited to a specific hospital in the Western Cape, it does highlight the need for ongoing research involving adolescents, their risks for mental illness and the impact of substance use particularly cannabis given the changing legislation in South Africa. It also emphasises the need for more adolescent focused awareness and prevention strategies, interventions and services.”