Study Identifies Link Between Cannabis Use Disorder and Schizophrenia

A collaborative study by researchers at the Mental Health Services in the Capital Region of Denmark and the investigators at the National Institute on Drug Abuse (NIDA) found a stronger link between cannabis use disorder and schizophrenia in young males than females.

The cohort study, published in Psychological Medicine, used data from the Danish national health registry. Information on individuals between 16 and 49 from 1972 to 2021, including their cannabis use disorder and schizophrenia status, was analyzed.

Across the 6,907,859 individuals in the study, there were 45,327 cases of schizophrenia. The data revealed that, in males, cannabis use disorder increased the probability of being diagnosed with schizophrenia by almost 2.5 times. Focusing on males between 16 and 20, the associated risk was even higher, with males with cannabis use disorder nearly four times as likely to have a schizophrenia diagnosis.

Comparatively, in females, cannabis use disorder only doubled the risk of schizophrenia overall. Focusing on the 16–20 group, the risk was slightly less than double.

According to a press release from the NIH, an estimated 15% of schizophrenia cases in 2021 among men between 16 and 49 could have been avoided by treating and managing cannabis use disorder. The percentage that could have been avoided for females was significantly lower at 4%.

“The entanglement of substance use disorders and mental illnesses is a major public health issue, requiring urgent action and support for people who need it,” said NIDA Director and study coauthor Nora Volkow, MD, in the NIH press release.

“As access to potent cannabis products continues to expand, it is crucial that we also expand prevention, screening, and treatment for people who may experience mental illnesses associated with cannabis use. The findings from this study are one step in that direction and can help inform decisions that healthcare providers may make in caring for patients, as well as decisions that individuals may make about their own cannabis use,” added Volkow.

Although this data provided some insight into the correlation between cannabis use disorder and schizophrenia, additional research is needed to quantify and understand the relationship holistically.