Just as the legalization of marijuana — for both medicinal and recreational use — was making huge inroads as a result of this week’s elections, a new study out of Norway is raising questions about marijuana’s psychological effects, suggesting a link between cannabis use and schizophrenia.
Researchers at the University of Bergen say cannabis use can cause a temporary cognitive breakdown that contributes to long term psychosis.
The small study included 26 patients with a history of schizophrenia. They were equally divided into two groups – those with a history of cannabis use and those who never used marijuana. All participants were given an audio test and MRI brain scan.
“While brain activity for both groups was similar, there are subtle differences between schizophrenia sufferers with a history of cannabis use and those who have never used cannabis” said Else-Marie Loeberg, lead author on the article and associate professor of Psychology at the University of Bergen. “These differences lead us to believe that the cognitive weakness leading to schizophrenia is imitated by the effects of cannabis in otherwise non-psychotic people.”
Researchers say the schizophrenics who had previously used cannabis had a higher level of brain activity and got more questions correct than the non-using schizophrenics. At the same time, however, they concluded that cannabis use may have contributed to the development of schizophrenia.
The findings support the theory that cannabis use puts people at risk of schizophrenia because it mimics the cognitive defect that is the primary risk factor for developing the disorder. Most of the patients started using cannabis before they became schizophrenic.
The study also suggests that cannabis users who have schizophrenic qualities do not experience the same neurocognitive shortcomings as other schizophrenia sufferers.
“Since THC [the active ingredient in marijuana] causes adverse cognitive short-term effects in vulnerable individuals, cannabis may cause a transient cognitive breakdown enabling a psychotic outbreak, but without the typical long-lasting neurocognitive vulnerability,” wrote Loeberg. “These changes may be more biochemical in nature, influencing the reactivity of the cannabinoid receptor systems.”
While further studies are needed to determine the exact cause for those changes, Loeberg says the cannabinoid receptor system is “widely expressed in the brain, especially in areas relevant to schizophrenia.”
The results of the study were published in Frontiers, a peer-reviewed journal of scientific research articles.