Researchers believe that developing schizophrenia and using cannabis may be due to similar genes. A new study published in Molecular Psychiatry suggests that people who are genetically predisposed to developing schizophrenia may also have the propensity for cannabis use, influenced by the same set of genes.
The study is a collaboration between King’s College London and the Queensland Institute of Medical Research in Australia, partly funded by the UK Medical Research Council (MRC).For years researchers have linked the use of cannabis as a risk factor for developing schizophrenia.
Experiments showed that people who used cannabis more frequently had greater chances of experiencing schizophrenic episodes than those who did not. But the role of genes related to schizophrenia and cannabis use was not well established until now. This new study suggests that there may be some genetic correlation between the two but it does not rule out the use of cannabis as a factor in developing schizophrenia.
Cannabis, more commonly known as marijuana, is a depressant drug that lowers neurotransmission levels, which means it slows down the messages travelling between the brain and the body thus develops depressing arousal or stimulation. Long term use of cannabis is known to cause memory loss, learning difficulties, mood swings and lowered sex drive, among others. It is the most widely used illicit drug in the world and the WHO estimates that about 147 million people, 2.5% of the world population, consume cannabis. People suffering from schizophrenia use it more than the general population.
Schizophrenia is a common and severe psychiatric disorder that affects around one in 100 people. People who use cannabis are about twice as likely as those who do not develop it.
Schizophrenia is characterized by visual and auditory hallucinations. According to estimates, 1 in every 100 people suffers from this condition. Research has shown that people with schizophrenia are more likely to use marijuana and that the drug users have a higher risk of developing the disorder. A causal link between the two hasn’t been established yet.
“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,” said Robert Power, lead author from the MRC Social, Genetic and Developmental Psychiatry (SGDP) Centre at the Institute of Psychiatry at King’s.
The disorder typically begins in late adolescence or early adulthood and its most common symptoms are disruptions in thinking, language and perception. It often includes psychotic experiences such as hearing voices or delusions.
While the exact cause is unknown, research suggests a combination of physical, genetic, psychological and environmental factors can make people more likely to develop it.
Previous studies have found a number of genetic risk variants associated with schizophrenia, each of which slightly increases a person’s risk of developing the condition.
For the study, researchers assessed 2,082 healthy individuals out of which 1,011 had used cannabis. Each individual’s ‘genetic risk profile’ was measured. This pointed out the number of schizophrenia related genes that each person carried. It was found that people who carried the schizophrenia gene were more likely to use cannabis and use it in greater quantities than those who were not genetically predisposed to developing schizophrenia.
“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 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.”