Fears that cannabis causes irreparable harm to teenager’s brains have been stoked by trials which “overstated” the effects on intelligence and other functions, according to a review which found little ill-effect after three days abstinence.
Studies have shown it is 114 times less harmful than alcohol, but marijuana’s impact on adolescents’ brain development and mental health is a major concern for policy makers in debates over legalisation.
This is a key time developmental period and studies have found negative impacts on attention, learning, memory and organisation in heavy or frequent cannabis users.
But it now appears that these studies may have just been identifying impairment caused by residual effects of the drug or withdrawal symptoms.
A meta-analysis by University of Pennsylvania researchers looked at 69 studies, which all tested the impact of marijuana smoking in adolescents and young adults, and found little to no long-term harm.
Although it did not look at mental health impacts, such as psychosis, the authors of the study published in the journal JAMA Psychology today, found the “persistence and magnitude of impact” on teenagers had been overblown.
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