A method of treating ASD (autism) in a patient in need thereof comprises administering a botulinum toxin to the patient. The botulinum toxin may be administered by subcutaneous/intradermal injection. The subcutaneous/intradermal injection may be administered to and/or around the vicinity of a trigeminal nerve, a cervical nerve, a thoracic nerve, a lumbar nerve, and a sacral nerve of the patient. In infants or toddlers—；from about 1 to 5 year olds, it is used to prevent or minimize damage to the developing brain； in older children and adult Autism Spectrum Disorder (ASD) patients, it will be used to reduce or eliminate their symptoms.
