Recent research suggests that there may be a link between cannabis use and an increased risk of developing schizophrenia symptoms. Prof. Marcus Menuafo, a team member from the School of Experimental Psychology at Bristol University in the United Kingdom hypothesized, "There is a growing consensus that cannabis use might increase the risk of developing schizophrenia. Our results support this, but also suggest that those at increased risk of schizophrenia may be more likely to try cannabis in the first place." Dr. Suzi Gage, a member of the team further explains the study that was conducted using Mendelian Randomization technique. This technique was chosen to utilize publicly available data to investigate causation relations between potentially modifiable risk factors and health outcomes from observation data as the team predicated those who are cannabis users are more likely to be genetically or biologically different than those who are not in a multitude of ways.
Findings from the study revealed that "an individual who is more likely to smoke cannabis has at most a 24% higher relative risk of suffering from schizophrenia compared with an individual with a low probability of smoking cannabis." People with a risk of schizophrenia may be more likely to use the drug because of the effects of THC within marijuana. The effects of the drug could relieve particular behaviors or symptoms of the disease within individuals.
Another study conducted on this topic is from researchers at the Tel Aviv University in Israel. This study was conducted using a mouse model with a strain of mice containing a mutant DISC-1 gene to observe the effects of THC on those who have a genetic susceptibility to developing schizophrenia. The mice were exposed to levels of THC at a point that could be compared to humans being exposed in their adolescence. Neurological biochemical analysis and behavioral tests were performed on the mice and results showed that cannabis is more likely to produce long-term psychiatric effects in individuals who are more genetically susceptible. "Young people who have family history of psychiatric conditions or have responded strongly to drugs previously should be particularly cautious around marijuana during their adolescence," warn researchers.
Statistics from the National Institute of Drug Abuse (NIH) state that around 44% of 12th graders have used marijuana in their lifetime. Along with approximately 12.8 percent of 8th graders have used the drug, with 0.7 percent using it daily. Research is showing a link between the effects and usage of marijuana in those are already at risk from a family history of psychotic disorders. While it is clear that genetic vulnerabilities play a part in these studies, researchers are also examining factors such as the age in which users were first exposed to marijuana and how often it was consumed and at what levels.
While more research and data need to be collected to argue a link between cannabis use and psychiatric conditions, the current studies can add weight to the hypothesis that those in adolescences with a genetic susceptibility to schizophrenia need to be careful to the exposure of cannabis.