It’s a lot easier to treat a disorder that has a known cause than one that doesn’t. Unfortunately, there is no one cause for autism, which makes it difficult to engineer targeted medications.
Instead, a variety of factors contribute to the development of autism: genetic mutations, environmental factors (e.g., pesticides, prenatal drug exposure, parental age) or a combination. The wide range of contributing factors underscores why autism is considered a spectrum with symptom severity ranging from mild to severe. This makes pharmacological treatment of autism particularly difficult. However, accumulating evidence suggests that in many cases of autism, there’s a reduction in the brain’s “inhibitory tone” (see below). This suggests that cannabis-based medications, particularly CBD-rich preparations that enhance the brain’s inhibitory signaling, may be a potential autism treatment.
Understanding Autism and Epilepsy
Reduced inhibition in the brain doesn’t just cause the defining symptoms of ASD, but can contribute to a host of comorbid disorders. For instance, between a quarter and half of individuals with ASD also have epileptic seizures. The comorbidity between epilepsy and ASD reflects a tipping in the brain’s excitatory/inhibitory balance towards excitation. Seizures result when the balance between the brain’s excitatory function and the brain’s inhibitory function shifts too heavily towards excitation. Epilepsy reflects a chronic imbalance that results from a permanent shift towards excitation.
One of the biggest questions regarding the feasibility of treating ASD in epileptic patients is whether it’s too late. Seizures can wreak havoc on the brain and alter the way in which neurons communicate and connect with one another and can rewire the brain. Is it seizures early in one’s life that cause ASD or is ASD the result of aberrant brain activity, like a reduction in the strength of the brain’s inhibition? This is a critical question because if early-life seizures rewire the brain and cause ASD, then it may be too late for pharmacological intervention; cannabis, for all it may be good for, can’t reverse these effects. However, if ASD, in some cases, is merely the result of an imbalance in brain function, then there’s hope.
How Cannabidiol (CBD) May Help Autism
The successful Phase III clinical trial demonstrating CBD’s antiepileptic effects in children with treatment-resistant epilepsy was exciting news for the epilepsy and medicinal cannabis communities. However, it did not address whether CBD treatment was effective at combating any other aspects of the disorder, like ASD.
Over the last couple of years, my lab has been researching CBD’s ability to treat seizures and autism in our mouse model of ASD and epilepsy. In a recent study, we present the first pre-clinical evidence that CBD can effectively treat autism in these mice.
How do you measure autism behaviors in mice? There are several tests that scientists commonly use to model social behavior. One test measures the time spent socially interacting with another mouse. When compared to time interacting with an inanimate object, normal developing mice show a strong preference for interacting with the mouse compared to the object. Mouse models of autism are indifferent about spending time interacting with a mouse versus an object. However, when given CBD, our mice gained a preference for socially interacting with the mouse. This test demonstrated that CBD improves social interaction deficits consistent with those seen in children with ASD, but it didn’t inform us of CBD’s effects on the quality of the interaction.
To gain insight into the qualitative elements of social interaction, we placed two mice in a square testing chamber simultaneously and allowed them to freely explore the chamber and interact with each other. In this test, ASD mice would frequently dart away from their social interaction and huddle in the corner of the chamber. We interpreted this to be a measure of social anxiety, which was likely, in part, driven by overwhelming sensory stimuli. CBD was able to normalize this abnormal escape behavior. These results reveal CBD’s potential to reduce autism-like impairments in social interaction and social anxiety that are caused by impaired inhibitory GABAergic signaling in the brain, which is a common underlying feature of ASD.
These improvements in social behaviors were associated with CBD’s ability to enhance inhibitory brain function by increasing the activity of the neurons that regulate the level of inhibition in the brain. By restoring this excitatory/inhibitory balance in the brain, CBD can reduce seizures and normalize social behavior…at least in mice.
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