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Cannabis Use May Increase Risk of Certain Psychotic Experiences, Study Finds

By Alexander Beadle

Published: May 13, 2022   
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According to a new study from scientists at the University of Cologne, frequent cannabis use may be associated with an increased risk of experiencing certain delusions, such as persecutory delusions or the idea of others hearing your own thoughts.

Published this month in Scientific Reports, the study also found that a younger age of cannabis use initiation was associated with increased irritability and experiencing visual hallucinations.

Based on their findings, the University of Cologne researchers concluded that different cannabis use characteristics uniquely contribute to the risk of developing specific psychotic symptoms. The research team suggest that preventative campaigns focused on youth cannabis could play an important role in combating some of these risks.

Frequent cannabis use associated with certain delusions

While several studies have suggested that cannabis use may put individuals at a higher risk of developing a psychotic disorder, the average cannabis user is still relatively unlikely to go on to be diagnosed with such a condition. However, it is important that research continues to investigate which aspects of cannabis use might be particularly potent at increasing this risk for psychosis.

In the study, the researchers used a network model to examine the relationship between two cannabis use characteristics – age at which cannabis was first used and the cumulative lifetime uses of cannabis – and a number of psychotic experiences, mood factors, and known childhood risk factors in cannabis users. This included reports of hallucinations, delusions, mania, depression, and childhood trauma.

In the network model, each of these variables were represented by stationary “nodes” on a diagram. Lines, also known as edges, were drawn between each node to reflect the association between each variable as determined by a statistical analysis model. The result was a visual interpretation of the relationship between many different characteristics, symptoms, experiences, and demographic factors.

The study focused on a subset of more than 2,500 responses to the National Comorbidity Survey. All the participants in this subset reported having used cannabis at least once in their lives, were aged between 15 and 40 years old, and had completed a subsection of the survey that asked about risk factors in more detail.

Using this network approach, the researchers found that higher lifetime cannabis use frequency was associated with more reports of certain delusions, such as believing others can hear your thoughts, feeling as though you are being spied on or followed, and hearing disembodied noises and voices. The higher the cumulative number of lifetime cannabis uses, the more likely these experiences became.

Early onset cannabis use linked to hallucinations and irritability

The network model also revealed several associations between age at the initiation of cannabis use and other unique psychotic symptoms. The younger an individual was when they began using cannabis, the more likely they were to experience visual hallucinations and report general irritability.

Early risk factors such as childhood abuse were also associated with younger ages of cannabis use initiation, but not a higher frequency of cannabis use. More generally, there was a strong link between earlier cannabis use and greater lifetime cannabis use.

The University of Cologne researchers say that their study is significant as it provides a large amount of evidence showing that cannabis not only increases the risk of psychotic symptoms in those already diagnosed with a psychotic disorder, but also increases the risk for psychotic experiences in the broader non-clinical population. It also suggests that early and frequent cannabis use could have different relationships with different psychotic experiences, and so campaigns focused on preventing youth cannabis use may be an important harm reduction tool.

The researchers also note several limitations with the study. For one, given the cross-sectional nature of the study, it is not strictly possible to determine the mechanism behind the discovered associations. As such, there is a possibility that it is the psychotic experiences in adolescence that may drive a younger initiation of cannabis use. Although, judging by previous research, this appears unlikely.

Additionally, the National Comorbidity Survey was carried out between 1990-1992 and cannabis potencies and use patterns have changed significantly since then. Similar investigations on a more modern data set could be a valuable way to expand upon this initial network research.

Cannabis and psychosis

While the relationship between cannabis and psychosis is known to exist, relatively little is still really known about how these two factors influence the other.

Recently, researchers from King’s College London analyzed data from the UK Biobank database and found strong associations between self-reported cannabis use frequencies and all types of self-reported psychotic experiences. After studying participant DNA data, they also found that cannabis users with higher genetic risk scores were significantly more likely to experience hallucinations, delusions, and other general psychotic episodes, raising the possibility that there could be a genetic component to this relationship.

But while cannabis appears to increase the risk of psychosis, the cannabinoid CBD may have an antipsychotic effect. In studying the brains of young people after taking a single dose of CBD, researchers have found heightened activity in two regions of the brain that are often under-activated in individuals with schizophrenia.


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