Smoking cannabis regularly during adolescence can cause a decrease in intellectual abilities in adulthood. This is what a study published Monday by the journal Proceedings of the U.S. National Academy of Sciences of the USA shows .
Research conducted in New Zealand with 1000 respondents taking into account individuals aged 25 was used to compare their intelligence quotient (IQ) at age 13 and at age 38, some being regular users of cannabis, even after 20 years or 30 years, others are not. At the end of the period, a difference of eight points widened between smokers and others, says Madeleine Meier, a psychologist at Duke University, North Carolina (southeast). She is the lead author of the study published in the Proceedings of the National Academy of Sciences. Yet, “IQ is supposed to be stable as we get older,” she said. For people who have never smoked cannabis, their IQ was even slightly increased a few tenths of points. “We know that IQ is a strong determinant for access to university, earned income throughout life, access to employment and job performance, “says researcher.
Someone who loses eight IQ points in his teens and twenties may find themselves at a disadvantage compared to their peers of the same age for many major aspects of life. And for many years, she says, noting that the significant difference is not due to other factors (education, alcohol, other drugs, etc.).. Marijuana users also showed lower memory capacity, concentration and alertness, according to the study. Those who slowed their consumption the year before their 38-year time of the second test, did not mean better results. Conversely, smokers who started only in adulthood did not suffer from such an intellectual gap with non-smokers. “Adolescence is a very sensitive period of brain development,” says the psychologist. Using substances that act directly on the young mind can disrupt normal brain processes, she says. By cons, this study did not evaluate the effects of a shutdown or slowdown of consumption earlier in life, and does not specify either, the quantities consumed.