June 18, 2021 – At least so far, the currently limited research base does not establish that cannabis has additional adverse effects on brain development or functioning in adolescents or young adults with attention-deficit/hyperactivity disorder , concludes a review in the July/August issue of Harvard Review of Psychiatry.
While ADHD is clinically defined to have impairments in cognitive functioning, cannabis use by itself is also associated with cognitive impairments: “he evidence to date does not clearly support either an addictive effect or an interaction – whether protective or harmful – with cannabis use,” according to the study by Philip B.
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.
Out of hundreds of initial “hits,” the search identified just 11 studies assessing any type of neurodevelopmental outcome in adolescents or young adults with ADHD who did use cannabis compared with those who did not use cannabis.
Given the limitations of the studies, the authors stress that these findings must be considered with caution and that it was impossible to determine whether or not these findings reflect causal relationships.
Functional imaging studies also reported differences in cannabis users with ADHD.
Four studies looked at the results of neuropsychological tests or questionnaires in young people with ADHD who did and did not use cannabis.
“Surprisingly, as cannabis use demonstrates clear and consistent adverse effects on cognition as measured by neuropsychological task performance, no study identified a significant differential impact of cannabis use on these measures for individuals with ADHD compared to non-users,” Dr.
Future studies may provide more definitive answers – particularly the ongoing “ABCD” study, which will provide long-term data on more than 10,000 participants followed up from age 10 to 20.
The Harvard Review of Psychiatry is the authoritative source for scholarly reviews and perspectives on a diverse range of important topics in psychiatry.
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