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Cannabis could cause schizophrenia, psychiatrist cautions

Schizophrenia is present in about one per cent of the population

Anton Grech: “I advise people not to consume the plant, especially if they have familial history of schizophrenia.” Photo: Jonathan Borg

Anton Grech: “I advise people not to consume the plant, especially if they have familial history of schizophrenia.” Photo: Jonathan Borg

Cannabis could cause serious mental illness, a top psychiatrist has warned.

“Schizophrenia is very severe and I believe that whoever uses cannabis should be aware they could get the condition. I advise people not to consume the plant, especially if they have familial history of schizophrenia,” Anton Grech, clinical chairman of the Department of Psychiatry within the Ministry of Health, said.

Schizophrenia is considered a chronic and severe psychiatric condition.

Any mental health hospital, including Mount Carmel, dedicates 70 per cent of its efforts on inpatient care of the condition.

Schizophrenia is present in about one per cent of the population, that is, about 4,000 Maltese people.

About 100 new cases are diagnosed every year in Malta but the percentage of people genetically predisposed to the disease remains unknown. Dr Grech spoke to this newspaper as colleagues in London work on formulating blood tests that would determine whether a person is predisposed to developing the disease if s/he smoked cannabis.

In Malta, research will soon be looking into how to effectively persuade schizophrenia patients to stop using cannabis on grounds that the methods used so far have remained ineffective.

A debate on the recreational use of cannabis could soon start in Malta in the wake of an electoral pledge by the Labour Party.

Dr Grech insisted that, for the time being, he would only be commenting as a psychiatrist and a scientist who carried out research about cannabis. He does not yet want to take sides and prefers to call for an informed debate that is based on scientific proof.

Someone might have the gene in him but illness is never triggered

Together with colleagues both in Malta and the UK, he has published several papers on the link between psychosis and cannabis. His doctorate specifically focused on the interaction between genes and the environment and on how cannabis could cause schizophrenia.

Research in Malta and the UK has shown that, despite cultural differences in other substance abuse, such as alcohol and heroin, those suffering from schizophrenia in both two countries use cannabis more than the general population.

Further research in Sweden, Denmark and Germany confirmed that those who smoked cannabis had a higher risk of being diagnosed with schizophrenia.

Meanwhile, among those who already suffered from schizophrenia, those who smoked cannabis experienced an earlier onset of the illness. Dr Grech’s own research over four years showed that the longer a person with schizophrenia consumed cannabis, the worse the condition got.

He pointed out that having a genetic predisposition to schizophrenia did not mean that one would definitely be diagnosed with the disease. If predisposed people did not consume cannabis, they could actually never suffer from the disease, he added.

“It is environmental circumstances that precipitate the illness. This means that if you are predisposed, then something – such as stress or cannabis – could trigger schizophrenia. That is, someone might have the gene in him but the illness is never triggered.”

Dr Grech noted that there was a particular component that could actually be beneficial for mental health. However, scientists had not yet figured out how to extract this.

Cannabis had several components, with the two most common ones being THC, which caused psychosis, and CBD, that could be beneficial for mental well-being, he said. The problem was that CBD extracts still had traces of THC.

Dr Grech compared this to snake venom, which has been imperative for the development of blood thinning and anti-hypertensive treatment. Sub-components of the venom proved beneficial, however, snake venom on the whole remained dangerous.

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