Psychotic-like experiences and cannabis use in adolescents from the general population.

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.