HQ Team
May 8, 2023: At least 30% of cases of schizophrenia in young adults could have been staved off in Denmark by preventing cannabis use disorder, a study of more the six million people revealed.
“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 Nora Volkow, director at the National Institutes of Health and study coauthor of the research.
“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 health care providers may make in caring for patients, as well as decisions that individuals may make about their cannabis use,” she said in a statement.
The study was done along with the National Institute of Drug Abuse and Mental Health Services in Denmark. It analyzed detailed health records spanning five decades, representing 6.9 million people.
21-30 age group
The association of schizophrenia with cannabis use disorder was stronger in young men of the 21-30 age group.
Substance use disorders are chronic, treatable conditions from which people can recover. In 2020, over 40 million people in the United States had at least one substance use disorder.
Substance use disorders are partly defined by continued substance use despite negative consequences. They are also relapsing conditions, in which periods of abstinence can be followed by a return to use. Stigma can make individuals with substance use disorders less likely to seek treatment.
Schizophrenia is a serious mental illness that affects how a person thinks, feels, and behaves. People with schizophrenia may seem like they have lost touch with reality, and the symptoms of schizophrenia can make it difficult to participate in usual, everyday activities.
Effective treatments are available for both cannabis use disorder and schizophrenia.
Near-daily cannabis use
Previous studies indicated that rates of daily or near-daily cannabis use, cannabis use disorder, and new schizophrenia diagnoses are higher among men than women, and that early, frequent cannabis use is associated with an increased risk of developing schizophrenia.
Few studies have examined differences in the relationship between cannabis use disorder and schizophrenia across different sex and age groups at the population level.
To address this gap, the investigators analyzed data from nationwide health registers in Denmark, between 1972 and 2021.
Using representative data, the researchers investigated how the associations between cannabis use disorder and schizophrenia varied by different sex and age groups, and how these differences changed over time.
The authors said that cannabis use disorder appeared to be a major modifiable risk factor for schizophrenia at the population level, particularly among young men.
Consistent increase
The study also adds to existing evidence suggesting that the proportion of new schizophrenia cases that may be attributed to cannabis use disorder has consistently increased over the past five decades.
The authors note that this increase is likely linked to the higher potency of cannabis and the increasing prevalence of diagnosed cannabis use disorder over time.
“Increases in the legalization of cannabis over the past few decades have made it one of the most frequently used psychoactive substances in the world, while also decreasing the public’s perception of its harm,” said Carsten Hjorthøj, PhD and lead author of the study and associate professor at the Mental Health Services in the Capital Region of Denmark, and at the University of Copenhagen.
“This study adds to our growing understanding that cannabis use is not harmless and that risks are not fixed at one point in time.”
Further research was needed to examine potential differences in the potency and frequency of cannabis consumption between young men and women and to examine the mechanisms underlying the higher vulnerability of young men to the effects of cannabis on schizophrenia.
