ISSN 1662-4009 (online)

ESPE Yearbook of Paediatric Endocrinology (2022) 19 14.8 | DOI: 10.1530/ey.19.14.8

ESPEYB19 14. Science and Medicine Risk and Outcome (5 abstracts)

14.8. Development over time of the population-attributable risk fraction for cannabis use disorder in schizophrenia in Denmark

Carsten Hjorthøj , Christine Merrild Posselt & Merete Nordentoft



JAMA Psychiatry. 2021 Sep 1;78(9):1013–1019. PMID: 34287621. doi: 10.1001/jamapsychiatry.2021.1471. https://jamanetwork.com/journals/jamapsychiatry/fullarticle/2782160

Brief Summary: This nationwide prospective registry study from Denmark in >7 million individuals reports that the proportion of schizophrenia diagnoses attributed to cannabis use disorder increased from 2% in 1995 to 8% in 2010.

In the last decades, the use and potency of cannabis products has increased. Daily cannabis use is associated with the development of schizophrenia-related psychoses, but it was under debate whether the association is causal. This nationwide Danish study provides evidence for causality by showing a time trend of increasing schizophrenia attributed to cannabis-use disorder, while considering a wide range of potential confounding factors, including individual and parental alcohol and other substance use disorder, and family history of psychoses. They calculated the ‘E-value’ to be as high as 5–10, indicating that a potential unmeasured confounder would need to have an unlikely high effect to explain the association between increasing schizophrenia with increasing cannabis use.

Rising incidence of schizophrenia due to cannabis use is likely driven by the increasingly heavy use of high-potency cannabis products, which became available over recent years. Several countries recently legalized cannabis, and many people may misinterpret this decision as meaning that cannabis use is harmless. Educating communities, especially adolescents and young adults, about the dangers of high-potency cannabis is important for preventing psychotic disorders.

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