For a more comprehensive discussion of autism and CBD’s ability to treat autism spectrum disorder, see my article on Leafly.
One of the most common brain characteristics of individuals with autism spectrum disorder (ASD) is reduced inhibitory brain signaling. This is the result of lower-than-normal levels of the inhibitory neurotransmitter, GABA. The reduction in inhibitory brain signaling contributes to numerous symptoms that characterize the disorder such as hypersensitivity to stimuli, abnormal social interaction behavior, and low sociability. Reducing the excitability of GABAergic neurons in mice brains leads to social deficits and restoring that excitability improves measures of social behavior.
Our work has revealed that cannabidiol (CBD) restores the excitability to inhibitory interneurons in the brain that are affected by genetic mutations that weaken the level of brain inhibition. By increasing inhibition, CBD improves levels of social interaction and normalizes social engagement characteristics.
There are several brain targets that may lead to CBD’s improvement in ASD-like behaviors. We find that CBD blocks the activity of a recently discovered receptor in the brain known as GPR55. Through this action, CBD increases the release of the inhibitory neurotransmitter, GABA. CBD may also act directly on the GABA receptors themselves to increase levels of brain inhibition. Additionally, CBD’s anxiolytic effects may improve some of the observed social behaviors by activating serotonin receptors in the brain. It could be one of these mechanisms, or a combination, that leads to CBD’s enhancement in brain inhibition that may treat social interaction deficits and abnormal social engagement characteristics in ASD.
Interestingly, anecdotal reports of humans using cannabis to treat severe forms of autism fall into two camps. Some find benefits with CBD, while others claim that CBD exacerbates symptoms. Instead, many find that THC is more effective at reducing ASD symptoms. What could be underlying this discrepancy?
The different outcomes between use of THC and CBD likely reflect genetically-determined differences in inhibitory brain function that characterize ASD. Reduced levels of brain inhibition may be caused by too little release of inhibitory neurotransmitters OR it’s mediated by excessive release of the brain’s excitatory neurotransmitters. Both mechanisms shift the brain’s balance towards excitation and can cause ASD symptoms, but they need to be pharmacologically targeted in different ways. In cases where the brain’s inhibitory system is weak, CBD may have the greatest benefit, while in cases when the excitatory system is too strong, THC may have the greatest benefit.
These different populations of anecdotal effects will be used to develop future studies and may enable genetics to inform the most efficacious treatment approach.