Genes that increase the risk of a person developing schizophrenia may also increase the chance they will use cannabis, researchers said on Tuesday after studying more than 1,000 users of the drug.
The results chime with previous studies linking schizophrenia and cannabis, but suggest the association may be due to common genes and might not be a causal relationship where cannabis use leads to increased schizophrenia risk.
Cannabis is the most widely used illicit drug in the world, and its use is higher among people with schizophrenia than in the general population. "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," said Robert Power, who led the study at the Institute of Psychiatry at King's College London.