The present invention is directed to a method of identifying autism spectrum disorder (ASD) phenotype 1 patients, wherein the method comprises: administering an Nrf2-activator to an ASD patient previously diagnosed with idiopathic ASD or a subject displaying clinical signs of ASD, and identifying the ASD patient as an ASD phenotype 1 patient if the patient shows a negative response after administration of the Nrf2-activator. Likewise, the present invention is directed to a method for classifying autism spectrum disorder (ASD) phenotype 1 patients, the method comprising: administering an Nrf2-activator to a subject, and observing if the subject shows a negative response after administration of the Nrf2-activator, in which the subject is a patient previously diagnosed with idiopathic ASD or a subject displaying clinical signs of ASD and in which the negative response supports classification of the subject as an ASD phenotype 1 patient.