A study published within the journal Schizophrenia Bulletin highlights that genetic risk aspects for schizophrenia can increase the potential of experiencing cannabis-related subclinical psychotic symptoms in regular cannabis users. 

Study: Associations Between Cannabis Use, Polygenic Liability for Schizophrenia, and Cannabis-related Experiences in a Sample of Cannabis Users. Image Credit: StunningArt / Shutterstock 

Background

Excessive cannabis use is thought to associate with psychotic-like experiences, schizophrenia symptoms, cognitive impairment, and emotional distress. Studies have shown that the administration of psychoactive constituents of cannabis can induce acute psychotic-like experiences, including unusual thoughts, paranoia, disorganized considering, and in some rare cases, auditory and visual hallucinations.

The chance of developing schizophrenia symptoms on account of cannabis use is partly influenced by genetic aspects. Recent evidence has shown that individuals with higher genetic susceptibility to schizophrenia have the next risk of developing psychotic-like experiences on account of cannabis intake.   

In the present study, scientists have investigated whether genetic risk for schizophrenia is related to cannabis intake-related psychotic-like experiences, including hallucination, paranoia, depression, cognitive difficulties, and impaired social interaction.

Study design

The study was conducted on a complete of 4,832 individuals partially ascertained for alcohol use disorder. Amongst enrolled participants, 74% met the lifetime criteria for alcohol use disorder, and 70% met the lifetime criteria for cannabis use disorder.

Five self-reported cannabis-related experiences were assessed within the study, including hallucination (audio, visual, and olfactory), paranoia, depression, cognitive difficulties, and impaired social interaction. Polygenic risk scores for schizophrenia were calculated using recent databases.

Statistical analyses were conducted to find out whether polygenic risk for schizophrenia is related to cannabis-related experiences in individuals who reported using cannabis at the least 11 times.

Vital observations

A high prevalence (70%) of cannabis use disorder was observed within the study population. Amongst them, 40% had mild, 25% had moderate, and 35% had severe cannabis use disorder. The typical age of first-time cannabis use was 16 years. About 75% of the enrolled participants reported using other illicit drugs.

A major positive association was observed between polygenic risk for schizophrenia and cannabis-related paranoia, depression, impaired social interaction, and cognitive difficulties. This association remained unchanged even after adjusting for duration of day by day cannabis use, cannabis use disorder, and age at first-time cannabis use. Conversely, cannabis-related hallucination showed the bottom association with polygenic risk for schizophrenia.

A major association between lifetime diagnosis of cannabis use disorders and earlier age at first-time cannabis use was observed with reporting of cannabis-related experiences. Aside from hallucination and paranoia, all other cannabis-related experiences showed significant associations with the duration of day by day cannabis use. Furthermore, a robust association was observed between the severity of cannabis use disorder and endorsing the next variety of cannabis-related experiences.

The evaluation conducted after adjusting for cannabis use disorder showed a robust association between polygenic risk scores for schizophrenia and all cannabis-related experiences except hallucination. Polygenic risk scores also showed a major association with endorsing the next variety of cannabis-related experiences. The very best association of schizophrenia polygenic risk rating was observed with cannabis-related cognitive difficulties.  

The evaluation conducted after adjusting for age at first-time cannabis use and diagnosis of alcohol use disorder revealed a robust association between polygenic risk rating for schizophrenia and all cannabis-related experiences except paranoia.

The study also included a separate group of 1,446 individuals with opioid use disorder and genetically unrelated control individuals with minimal or no lifetime opioid misuse. On this study group, no significant association was observed between polygenic risk rating for schizophrenia and cannabis-related experiences. Nonetheless, the patterns of associations were much like that observed in individuals with alcohol use disorder and cannabis use disorder.

Study significance

The study reveals that regular cannabis users with higher pre-existing genetic susceptibility to schizophrenia are at higher risk of experiencing cannabis-related psychotic experiences, including hallucination, paranoia, depression, cognitive difficulties, and social withdrawal. Furthermore, excessive and early-onset cannabis users usually tend to report unusual cannabis-related experiences.

As mentioned by the scientists, the study involved ascertained individuals with a high prevalence of cannabis use disorder and use of other illicit drugs. This makes it unclear whether these findings might be generalized to the population at large.