Methods of treating autism include applying at least one stimulus to a stimulation site within the brain of a patient with an implanted stimulator in accordance with one or more stimulation parameters. The stimulus is configured to decrease neural activity within at least a portion of the brain to treat autism. Systems for treating autism include a stimulator configured to apply at least one stimulus to a stimulation site within the brain of a patient in accordance with one or more stimulation parameters. The stimulus is configured to decrease neural activity within at least a portion of the brain to treat autism.