The Endocannabinoid System’s Role in ADHD: Insights from a Comprehensive Scoping Review

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A recently published review examined the possible connections between the endocannabinoid system (ECS) and attention deficit hyperactivity disorder (ADHD) symptoms. The review, “Attention Deficit Hyperactivity Disorder, Cannabis Use, and the Endocannabinoid System: A Scoping Review,” was published in Developmental Psychobiology in September 2024. Noting the prevalence of cannabis use and misuse in individuals with ADHD, and the lack of understanding between cannabis use and ADHD pathophysiology, researchers conducted a scoping review on preclinical and clinical evidence on the ECS and ADHD. No specific reviews have been done yet in this area, they noted.

To examine the potential therapeutic effects and influence of the ECS, researchers searched PubMed, PsyINFO, EMBASE, and the Cochrane Library for studies published up to March 2022 and examined data from relevant clinical and preclinical studies. They closely examined 13 of the studies. Data from five preclinical studies, five clinical studies examining effects of cannabis on cognition, and two clinical studies examining effects of cannabis on ADHD symptoms were presented in tables.

Data from the preclinical studies suggested that the ECS plays a role in regulating neurocognitive functions that are dysregulated in ADHD. In particular, the studies suggested:

• Persistent adolescent-like behavior in adults is mediated by Cannabinoid 1 receptor (CB1R) function.
• The ECS modulates impulsivity, particularly inhibitory control, which provides a possible target for managing attention-related deficits.

Data from clinical studies was sparse, the researchers noted, and should be interpreted with caution. The data focused on the ECS and executive function, inhibition control and impulsivity, and ADHD symptomatology. Some of the findings from the data included:

• THC administration impaired executive function during a continuous performance task, suggesting ECS involvement in ADHD-related abnormal default mode network (DMN) activity.
• ADHD diagnosis impacted executive function more significantly than cannabis use.
• Some surveys showed that cannabis use improved some ADHD symptoms, yet other studies found no improvements in symptoms when using cannabinoid medications.

“Findings from this review suggest both potential therapeutic benefits and detrimental drug interactions for individuals with ADHD using cannabinoids,” researchers noted in the concluding remarks. “Despite the growing popular opinion that cannabis and cannabinoids may be a therapeutic agent for ADHD symptoms, several critical questions remain unanswered. More rigorous and comprehensive studies are needed to fully understand the safety and efficacy of cannabinoid therapies in individuals with ADHD.”

The research received funding from the National Institutes of Health and two internal grants from Thomas Jefferson University.

Reference

1. Ryan, JE.; Fruchtman, M.; Sparr-Jaswa, A.; Knehans, A.; Worster, B. Attention Deficit Hyperactivity Disorder, Cannabis Use, and the Endocannabinoid System: A Scoping Review. Developmental Psychobiology. (2024). doi:10.1002/dev.22540