Marijuana Use Not Associated with Psychosis in Young People Finds Study

A history of marijuana use in young people is not independently associated with an increased risk of psychosis, according to a new study published in the journal Adicciones, and published online by the U.S. National Institute of Health.

“The purpose of this study was to analyze the relationship between psychotic-like experiences and cannabis use in a representative sample of adolescents from the general population”, states the study’s abstract. “A total of 1,588 students (M=16.13 years, SD = 1.36), 739 men (46.5%), selected by stratified random sampling by conglomerates from 98 classes in 34 schools participated in the survey.”

For the study, researchers with the University of La Rioja in Spain explored the relationship between psychotic-like experiences and cannabis use in a representative sample of over 1,500 Spanish adolescents.

According to NORML, they reported that initially identified associations between cannabis use and psychosis were no longer present once researchers controlled for confounding variables, such as socioeconomic status, alcohol use, tobacco smoking, and comorbid psychopathology.

Authors concluded, “In this study, it was found that after controlling for the effect of the multiple relevant co-variables, the use of cannabis was not related to the frequency and distress associated with psychotic experiences reported by adolescents. … These results suggest that the relationships established between psychotic-like experiences and cannabis are complex and mediated by relevant variables.”

The full abstract of the study can be found below:

The purpose of this study was to analyze the relationship between psychotic-like experiences and cannabis use in a representative sample of adolescents from the general population. A total of 1,588 students (M=16.13 years, SD = 1.36), 739 men (46.5%), selected by stratified random sampling by conglomerates from 98 classes in 34 schools participated in the survey. The instruments used were the Prodromal Questionnaire-Brief, the Strengths and Difficulties Questionnaire, the Modified Substance Use Questionnaire, the Penn Matrix Reasoning Test, the Family Affluence Scale-II, and the Oviedo Infrequency Scale. Results showed that a percentage of adolescents reported psychotic-like experiences and/or cannabis use. Prior to controlling for multiple confounders (gender, age, socio-economic level, smoking, alcohol use, emotional and behavioral problems, and IQ), cannabis use was associated with psychotic-like experiences. After adjustment for confounders, psychotic-like experiences were not seen to be associated with cannabis use. Mediational analyses showed that emotional and behavioral problems mediate the relationship between cannabis use and risk of psychosis. It seems that once the effect of multiple confounding variables is controlled for, the use of cannabis increases the risk of comorbid psychopathology and this, in turn, increases the risk of psychosis. These results suggest that the relationships established between psychotic-like experiences and cannabis are complex and mediated by relevant variables. Further studies should examine this relationship in follow-up studies and gene-environmental designs.

The full text of the study, titled “Psychotic-like experiences and cannabis use in adolescents from the general population,” appears in the journal Adicciones.

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