People at a greater risk of developing schizophrenia are also more likely to try cannabis, according to new research. Scientists last year expressed their concerns over what they hypothesised was an increased risk of schizophrenia resulting from people trying marijuana.
However, researchers from Bristol’s School Of Experimental Pyschology found there to be stronger evidence for the opposite problem.
Dr Suzi Gage from Bristol’s MRC Integrative Epidemiology Unit said: ‘The evidence suggested that schizophrenia risk predicts the likelihood of trying cannabis.’
The findings support the idea people use marijuana to self-medicate pre-existing mental conditions, rather than the drug causing them in its own right.
Dr Gage added: ‘Our results don’t really allow us to accurately predict the size of the effect — they’re more about providing evidence that the relationship is actually causal, rather than the result of confounding or common risk factors.’
The causal link between those at risk of developing schizophrenia being more likely to indulge in the odd spliff is a significant finding, especially as it provides evidence running counter to the commonly-held belief weed causes mental health conditions.
Dr Gage commented on the method and said: ‘Our results use a novel method to attempt to untangle the association between cannabis and schizophrenia. While we find stronger evidence that schizophrenia risk predicts cannabis use, rather than the other way round, it doesn’t rule out a causal risk of cannabis use on schizophrenia.
‘What will be interesting is digging deeper in to the potential sub-populations of cannabis users who may be at greater risk, and getting a better handle on the impact of heavy cannabis use.
‘In this study we could only look at cannabis initiation. What would really help progress this research is to use genetic variants that predict heaviness of cannabis use, as it seems that heavy cannabis use is most strongly associated with risk of schizophrenia. Once genetic variants are identified that predict heaviness of cannabis use we’ll be able to do this.’