Cannabis use is likely to trigger schizophrenia in those at risk. According to a recent study involving experts from the Innsbruck University Hospital, cannabis is also highly dangerous after the first such episode and leads to a drastic increase in relapses.
“Cannabis use increases frequency of relapses”
“In patients who are in remission after a first episode of schizophrenia, schizophreniform or schizoaffective disorders, cannabis use increases the frequency of relapses,” wrote the team of authors, which also includes the psychiatrist and Rector of MedUni Innsbruck, Wolfgang Fleischhacker , heard, now in the Schizophrenia Bulletin (doi: 10.1093/schbul/sbad033). This applies both to patients who follow the therapy recommendations (especially taking antipsychotic medication) and to those who do not.
The international group of scientists with first author Linda Levi from the Sheba Medical Center in Ramat Gan in Israel analyzed the data from a European study on the first episodes of schizophrenic disorders. The treatment results were good overall. The scientists: “After ten weeks of antipsychotic treatment, 282 of 446 patients (63 percent) met the criteria for remission.” 134 of the patients without symptoms could be followed for one year. Among other things, the experts analyzed the temporal connection between cannabis use and signs of illness or relapses from various perspectives.
Effects of drug use examined
A clear effect of the use of narcotics was found. Compared to patients who did not use cannabis, those who used cannabis showed a 3.03-fold increased risk of recurrence. Even in patients who regularly took their antipsychotic drugs, the risk of recurrence was 2.89 times higher. So the antipsychotics could not offset the cannabis effect.
What the scientists emphasize in their summary: The temporal relationship showed that cannabis use always preceded a relapse. Use did not only appear when the relapse was already underway.
It has been known for a long time that frequent cannabis consumption can trigger psychotic illnesses, especially schizophrenia. “Among Swedish army recruits observed from 1969 to 1983 (…) heavy cannabis users were found to be three times more likely to develop schizophrenia than cannabis abstainers,” wrote Holly Elser and her co-authors in a recent study in JAMA Network Open (doi:10.1001/jamanetworkopen.2022.52689).