Plan B Forum

»Scientists have found people with a genetic pre-disposition to schizophrenia are also more likely to use cannabis


»Researchers examined 2,082 people - 1,011 of whom had used cannabis
»Each individual’s ‘genetic risk profile’ was measured
»This means the number of genes relating to schizophrenia were noted
»Study has implications for the economic and health impact of the drug
A number of scientific studies claim to have found a link between cannabis use and schizophrenia.

But a group of British researchers have now discovered cannabis smokers may be genetically more likely to suffer from the condition. This is the first time scientists have found the genes responsible for schizophrenia could make people more likely to use the drug.

‘Studies have consistently shown a link between cannabis use and schizophrenia,’ said Robert Power, a Phd Student from the Institute of Psychiatry at King’s College London. ‘We wanted to explore whether this is because of a direct cause and effect, or whether there may be shared genes which predispose individuals to both cannabis use and schizophrenia.’ Cannabis is the most popular illegal drug globally and statistics show that people with schizophrenia tend to be more likely to use it than the general population.

Schizophrenia affects around one in 100 people and individuals who use cannabis are thought to be twice as likely to develop the condition, with symptoms including delusions and hearing voices. Researchers examined 2,082 people - 1,011 of whom had used cannabis. Each individual’s ‘genetic risk profile’ was measured, meaning the number of genes related to schizophrenia that each individual carried.

It was discovered that people who had a genetic pre-disposition to schizophrenia were more likely to use cannabis. The study, which was published in the journal Molecular Psychiatry, also revealed that people who were genetically pre-disposed to the condition, smoked more than those without schizophrenia risk genes. Power said: ‘We know that cannabis increases the risk of schizophrenia. ‘Our study certainly does not rule this out, but it suggests that there is likely to be an association in the other direction as well - that a pre-disposition to schizophrenia also increases your likelihood of cannabis use. ‘Our study highlights the complex interactions between genes and environments when we talk about cannabis as a risk factor for schizophrenia. ‘Certain environmental risks, such as cannabis use, may be more likely given an individual’s innate behaviour and personality, itself influenced by their genetic make-up. ‘This is an important finding to consider when calculating the economic and health impact of cannabis.’

The results suggest that part of this association is due to common genes, but the researchers stress that they have not ruled out a causal relationship between cannabis use and schizophrenia risk.