New research suggests genes that increase the risk of developing schizophrenia also make one more likely to use cannabis.
Past studies have found a link between cannabis use and schizophrenia, but it has been unclear if cannabis use actually causes the disorder, a Kings College London news release reported. This new study suggests the link is genetic, but does not totally rule out a direct link between cannabis use and schizophrenia.
"Studies have consistently shown a link between cannabis use and schizophrenia. 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," Robert Power, lead author from the MRC Social, Genetic and Developmental Psychiatry (SGDP) Centre at the Institute of Psychiatry at King's, said in the news release.
Cannabis is the most widely used illicit drug, and use is even higher in schizophrenics. People who use cannabis are believed to be twice as likely to develop schizophrenia.
In the past researchers have identified a number of genetic risk variants that increase the risk of schizophrenia. The study looked at 2,082 healthy individuals, 1,011 of which had used cannabis, and identified how many of these risk factors each participant carried. The team found those who were more predisposed to schizophrenia were also more likely to use cannabis.
"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," Power said.
"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 [behavior] 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," he said.
