Using marijuana between once a week and every day increases the risk of a psychosis-like experience by 159 percent, the U.K. Daily Mail reported, citing a new study.
Researchers from the University of Montreal followed 4,000 13-year-olds for four years, having participants complete questionnaires about substance abuse and any psychotic experiences.
The study was published in the Journal of Child Psychology and Psychiatry, the Daily Mail reported.
Psychotic experiences are described as perceptual aberration — the feeling that something external is part of the body — and feelings of being unjustly and badly treated.
Other tests included cognitive tests including to assess their IQ, memory and stimuli response.
The researchers were concerned with the negative effects of marijuana on adolescents.
“Our findings conform that becoming a more regular marijuana user during adolescence is, indeed, associated with a risk of psychotic symptoms,” said lead study author Josiane Bourque, the Daily Mail reported.
Other findings included that marijuana abusers — using the drug between one and seven times — reduced a person’s ability to resist socially unacceptable behavior in response to particular stimulus and an increase in symptoms of depression.
“An increase in symptoms of depression — such as negative thoughts and low mood — could explain the relationship between marijuana use and increasing psychotic-like experiences in youth,” Ms. Bourque said, according to the Daily Mail.