Systems and methods for treating autism spectrum disorders (ASD) and related dysfunctions are disclosed. A method in accordance with a particular embodiment includes determining that a patient suffers from an autistic disorder and, based at least in part on the determination, selecting a cortical signal delivery site. The method can further include implanting an electrode within the patient's skull and external to a cortical surface of the patient's brain, and treating the autistic disorder by applying electrical signals to the implanted electrode in conjunction administering an adjunctive therapy to the patient.