The present invention is directed to a method for differentiating between ASD phenotype 1, phenotype 2 and other ASD patients, wherein the method comprises: administering an Nrf2-activator to a subject, and identifying the subject as an ASD phenotype 1 patient if the subject shows a negative response, as a phenotype 2 patient if he shows a positive response and as another ASD patient if he does not show a positive nor a negative response, wherein the subject is a patient previously diagnosed with idiopathic ASD or a subject displaying clinical signs of ASD. Likewise, the present invention is directed to an Nrf2-activator for use in differentiating between autism spectrum disorder (ASD) phenotype 1 patients, phenotype 2 patients and other ASD patients, wherein the Nrf2-activator is administered to a subject, wherein a phenotype 1 patient is identified by a negative response, a phenotype 2 patient is identified by a positive response and other ASD patients are identified by the absence of a positive and a negative wherein the subject is a patient previously diagnosed with idiopathic ASD or a subject displaying clinical signs of ASD.