Abstract: The present invention is directed to a method for the treatment of autism comprising administering to a person in need of such treatment a therapeutically effective amount of a lipid-soluble thiamine derivative. The lipid-soluble thiamine derivative is preferably tetrahydrofurfuryl disulfide (TTFD). TTFD administration methods may include suppository forms, transdermal carriers, such as gels, lotions, or creams; and oral carriers, such as tablets or capsules.