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Cannabis Use Disorders May Protect Digestive Health in People With Schizophrenia

By Alexander Beadle

Published: Mar 28, 2019   
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According to figures from the World Health Organization (WHO) and the United Nations Office on Drug and Crime (UNODC), cannabis is the most commonly used illicit drug globally. Just as within the healthy population, this same prevalence of cannabis use is also seen within the population of people who are affected by psychiatric disorders, such as schizophrenia. 

The majority of current research into the relationship between cannabis use and schizophrenia focuses on potentially detrimental effects, such as impaired cognition or a possible worse prognosis following diagnosis with schizophrenia. Though, interestingly, one 2015 study looking at the links between substance abuse and mortality, found that while people with co-morbid schizophrenia and cannabis use disorders were at an increased risk of all-cause mortality, they actually had a decreased risk of dying from disorders and diseases affecting the digestive organs. 

Cannabis is known to have an effect on digestive organs. In fact, the anti-inflammatory action of some cannabinoids has led to cannabis-derived medicines that are used to treat abdominal pain and diarrhea. Research has also indicated that cannabis may assist in the treatment of some gastrointestinal conditions, such as inflammatory bowel disease.

Further research into schizophrenia and the endocannabinoid system has revealed that it may be dysfunctional or disrupted in patients with schizophrenia. The endocannabinoid system is also known to be involved in a complex relationship with the body’s gastrointestinal tract. 

On account of these links and apparent relationships between schizophrenia, cannabis, and digestive health, a team of researchers from various institutions in Copenhagen, Denmark, have conducted a study investigating the association between cannabis use disorders and the development of disorders of the digestive organs in people with diagnosed schizophrenia versus a control group. The results of the study have recently been published in the journal Psychological Medicine.

Study of the Danish health registers

The researchers used anonymized data from nationwide Danish health registers to create two study populations. The first population contained all people born in Denmark since 1955 who had been diagnosed with schizophrenia in the secondary healthcare sector, as according to the Psychiatric Central Research Register. Data for the control groups came from the Danish Civil Registration System. Each schizophrenia case was matched with up to 10 controls, who had never been diagnosed with schizophrenia and were the same age and sex as the case patients at the time of their diagnosis. The data from these registers yielded 21,066 identified cases with schizophrenia, and 176,935 sex-and-age matched controls.

The patient data analyzed to investigate whether cases with schizophrenia were more likely than the control population to develop digestive problems. These health issues included cancerous and non-cancerous disorders of the digestive organs, inflammatory bowel diseases, gastrointestinal disorders, and problems with the liver and pancreas.

Statistical analysis suggests decreased risk of digestive organ disorders

When comparing the patients with schizophrenia against the control population in the initial analysis, it was observed that the people with schizophrenia appeared to be at a significantly greater risk of developing almost all types of disorder of the digestive organs apart from cancers and disorders exclusively affecting the liver or pancreas. 

For patients with schizophrenia, co-morbid cannabis use disorders were associated with an increased risk of developing any type of digestive organ disorder. An increased risk was also seen in the control population as all outcomes other than the development of an inflammatory bowel disease were more common in those with a cannabis use disorder.

But when key risk factors were accounted for, there was a marked decrease in the risk of developing gastrointestinal diseases, which was deemed statistically significant. Decreases in risk of developing inflammatory bowel disease and other serious disorders of the digestive organs were also seen, but these remained just above the conventional thresholds for statistical significance. 

Among the cases of schizophrenia there was also a statistically significant association between alcohol use disorders and an increased risk of all outcomes. A significant association was also seen between other substance abuse disorders and all outcomes, with the singular exception of inflammatory bowel disease risk. 

In the control cases with no schizophrenia diagnosis, alcohol and other substance abuse disorders were found to be associated with an increased risk of all potential outcomes, with the exception of inflammatory bowel disease which was just above the levels of statistical significance for both alcohol and other substance disorders. 

A possible explanation?

The Danish study clearly shows that cannabis use disorders in people with schizophrenia results in a marked decrease in the risk of developing functional gastrointestinal disorders, as well as a possible decrease in risk for other disorders of the digestive organs. This was not seen in the non-schizophrenia control data. 

The Danish researchers put forward several possible explanations as to why this observed association exists. Firstly, they discounted the suggestion that this perceived protective effect of cannabis use might be as a result of under-diagnosis, as a similar trend for reduced mortality from digestive organ disorders has also been observed in populations with schizophrenia and cannabis misuse problems.

But people with schizophrenia have been found to have a disrupted endocannabinoid system compared to individuals without schizophrenia. And their endocannabinoid system does have some effect on the body’s gastrointestinal tract. One theory that the researchers propose is that heavy cannabis use could partially counter some of this disruption, which could have the effect of reducing the risk of disorders related to the gastrointestinal tract. This would also explain why similar risk reduction isn’t seen in the control group, who would not experience the same endocannabinoid disruption. 

A second theory is that the endocannabinoid system might be interacting with other transmitter systems that are known to be disrupted in schizophrenia, which result in the same risk mitigation from digestive organ disorders. 

However, this study does have some notable limitations. For instance, the patient data only allows the study of substance abuse disorders rather than the study of any level of substance use, and there is a risk that more mild gastrointestinal disorders and substance misuse may not have been recorded in the secondary health sector registers. The patient data also does not indicate if or when any of these disorders went into remission, meaning it is impossible to determine if this response is dose-dependent. 

Still, this study is a first in linking cannabis to a potential decrease in risk from gastrointestinal and other digestive health issues in people with schizophrenia. While the previously observed links to an increase of all-cause mortality should encourage some caution, further research into the clinical cannabis use for treatment and prevention of digestive organ disorders in people with schizophrenia may be worth exploring. 

Alexander Beadle

Science Writer

Alexander Beadle has been working as a freelance science writer since 2017 and has covered the cannabis industry for Analytical Cannabis since 2018. He has also written for our sister publication, Technology Networks, and the cannabis industry consultant firm Prohibition Partners, among others. Alexander holds a Master's in Materials Chemistry from the University of St. Andrews, where he won a Chemistry Purdie scholarship, and conducted research into zeolite crystal growth mechanisms and the action of single-molecule transistors.


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