Abstract Background The pharmacological treatment for autism spectrum disorders is often poorly tolerated and has traditionally targeted associated conditions, with limited benefit for the core social deficits. We describe the novel use of a cannabidiol-based extract that incidentally improved core social deficits and overall functioning in a patient with autism spectrum disorder, at a lower dose than has been previously reported in autism spectrum disorder. Case presentation The parents of a 15-year-old boy, of South African descent, with autism spectrum disorder, selective mutism, anxiety, and controlled epilepsy, consulted a medical cannabis physician to trial cannabis extract to replace seizure medications. Incidentally, at a very...