U.S. researchers say there’s simply not enough information available yet to determine if using cannabis does or does not influence brain development or functioning in adolescents and young people with attention-deficit/hyperactivity disorder (ADHD).
That conclusion is part of a detailed new review published last week in the July/August issue of Harvard Review of Psychiatry.
“[T]he evidence to date does not clearly support either an addictive effect or an interaction — whether protective or harmful — with cannabis use,” write Dr. Philip Cawkwell of the Stanford University School of Medicine and his study colleagues.
Getting more confident about conclusions either one way or the other demands additional research “to clarify possible effects of cannabis on brain structure, function and behaviour in young people with ADHD,” according to Wolters Kluwer Health, which publishes the journal.
Trying to pin down the combined effects of cannabis use and ADHD in adolescence, investigators looked at 11 studies that assessed any type of neurodevelopmental outcome in the age group who did or did not use weed.
While “no study identified any additive or ADHD × cannabis use interaction on neuropsychological tasks of executive function,” notes the abstract, two “found adverse differential impacts of early-onset cannabis use in this population.”
Increased accessibility and legalization of cannabis in the U.S. is of concern given that “about one-fourth of teens with substance use disorder also have ADHD, while youth with ADHD are six times more likely to have drug or alcohol abuse,” notes the Wolters Kluwer press release.
Because both ADHD and cannabis use have been associated with cognitive impairments, it was suggested “youth with ADHD might be particularly vulnerable to effects of cannabis on cognitive function,” the statement adds.