Cannabis can cause schizophrenia. Why isn’t that part of the legalisation debate?

By October 13, 2020 Recent News

The SpinOff 14 October 2020
Our additional comment: Just as those who are being treated in the healthcare system have the right to give informed consent, those who are voting in the referendum are entitled to be informed of the link between cannabis and schizophrenia.

For many, a quick flick through these brochures could be the extent of their research on the proposed changes to cannabis law; others may have delved further into the pros and cons of legalisation on sites such as The Spinoff. Still, no matter how much attention a voter has paid to the issue, it’s likely they’ve seen no mention at all of one incredibly important factor: the link between cannabis and schizophrenia.

Schizophrenia is a form of psychotic illness which affects the way we think. It is characterised by a loss or re-interpretation of reality through delusions, hallucinations, and other bizarre thinking. Episodes of the illness are referred to as psychosis. Research shows a significant connection between schizophrenia and Tetrahydrocannabinol (THC), the chemical component responsible for cannabis’s psychological effects. This form of schizophrenia is also known as cannabis-induced psychosis.

According to Robin Murray, professor of psychiatric research at the Institute of Psychiatry at London’s Kings College, the risk of schizophrenia increases with the potency of the cannabis used: “if the risk of schizophrenia for the general population is about 1%, the evidence is that, if you take ordinary cannabis, it is 2%; if you smoke regularly you might push it up to 4%; and if you smoke ‘skunk’ (high-strength cannabis) every day you push it up to 8%”.

Auckland University psychiatry professor Graham Mellsop has further found that the proportion of patients diagnosed with schizophrenia is significantly higher in instances of prolonged illicit substance abuse than in prolonged alcohol abuse.

So why are the links between cannabis and schizophrenia not a greater talking point in this referendum?