Public health cannabis messages must highlight mental health risks - Psychiatrist

Tasleem Gierdien

Tasleem Gierdien

5 November 2025 | 9:40

As South Africa’s 'green economy' continues to expand, Dr Lisa Dannatt says public health messaging on cannabis should focus on the potential risks to the developing brain.

Public health cannabis messages must highlight mental health risks - Psychiatrist

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Has adolescent cannabis use increased in South Africa since decriminalisation?

Dr Lisa Dannatt, a subspecialist addiction psychiatrist working in private practice, and an honorary senior lecturer at the University of Cape Town in the Department of Psychiatry and Mental Health, says the answer is complex.

"We have no national data at this point in South Africa about adolescent cannabis use."

However, one of Dannatt’s studies examined data from adolescents aged 13 to 18 in a high-risk psychiatric ward. The research found a rise in the number of adolescents presenting with severe mental illness, alongside increased cannabis use.

"We definitely saw an uptick in cannabis use, with associated significant increase in substance harm, particularly psychosis."

Dannatt points out that cannabis has become increasingly appealing and accessible to young people, particularly in the absence of strong public health campaigns warning against its use.

"The messaging is attractive to the youth. The other gap in South Africa is that there was no co-occurring, public health campaign warning cautioning the youth around cannabis use and the risks for the youth."

Dannatt explains that the psychoactive component of cannabis is THC (tetrahydrocannabinol), a chemical compound that can be altered depending on how the plant is cultivated. The THC content also varies across different cannabis plants and products.

"The cannabis resins, oils, gels, gummies have much higher THC contents... probably 90% higher than the cannabis joints that we're familiar with – and the gummies, vapes and gels are far more appealing to the youth."

As South Africa’s 'green economy' continues to expand, Dannatt emphasises that public health messaging on cannabis should focus on the potential risks to the developing brain and mental health.

"Your brain is still developing up until the age of 25. You're forming all your neural pathways in your pre-frontal cortex – which will affect your mood, emotions, cognition... using cannabis early from multiple international studies has shown a drop in IQ, risk of psychosis, risk of mood disorders (including bipolar and depression), a risk of anxiety disorders and then a further risk of suicide."

"We think cannabis is safe because it is not lethal, but there is a significant mental health risk and mental health risk is always perceived as lower than physical health... the public health messages we need to start getting out there is the risk to your mental health."

To listen to Dr Lisa Dannatt in conversation with Lester Kiewit on CapeTalk's Breakfast show, click below:

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